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Kidney: Infection Imaging Pearls - Educational Tools | CT Scanning | CT Imaging | CT Scan Protocols - CTisus
Imaging Pearls ❯ Kidney ❯ Infection

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  • “The  most  common  cause  of  ascending  pyelonephritis  is  Escherichia  coli,  while  staphylococci  and  streptococci  typically  cause  pyelonephritis  via  the  hematogenous  route.  Well-established  acute  pyelonephritis  and  abscess  formation  can  be  readily  diagnosed  from  findings  on  CT  or  MR  images.  Imaging  findings  of  diffuse  pyelophritis  including  enlarged  kidneys  with  geographic  nephrographic  defects,  striated nephrogram, and perinephric fat stranding are well described  in  radiology  literature.  However,  solitary  or  multifocal  lesions  during  the  early  phase  of  pyelonephritis  or  focal  pyelonephritis  may  masquerade  as  tumors.  Clinical  symptoms  and  supportive  laboratory  findings  including abnormal urinalysis results allow a correct diagnosis to be made. While prompt treatment results in resolution of  renal  pseudomasses,  delays  in  diagnosis  and  institution  of treatment lead to progression to frank pyelonephritis and renal or perinephric abscess formation. Temporal changes in lesion size and morphology after antibiotic therapy provide confirmatory proof of diagnosis.”
    Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation
    Krishna Prasad Shanbhogue et al.
    RadioGraphics 2023; 43(12):e230071
  • “Renal  tuberculosis  (TB)  almost  always  occurs  owing  to  in-fection from Mycobacterium tuberculosis, although Mycobac-terium  bovis  may  be  rarely  involved.  Secondary  TB  occurs  owing to reactivation of latent infection after initial dissem-ination to diverse organs. Genitourinary tract TB may affect the kidneys and upper and lower urinary tracts. It may manifest after a variable latency of 5–40 years after initial in-fection (4). The diffuse miliary form of renal TB may be seen in patients with disseminated systemic infection. The genitourinary  tract  is  one  of  the  common  extrapulmonary  sites  of TB, accounting for 15%–20% of cases. It commonly affects adults in the 2nd to 4th decades of life. Dysuria, flank pain, hematuria, and sterile pyuria are common clinical manifestations.”
    Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation
    Krishna Prasad Shanbhogue et al.
    RadioGraphics 2023; 43(12):e230071
  • “Diffuse  wall  thickening  and  strictures  of  the  upper  urinary  tract,  including  the  characteristic  pelvic  and  infundibular  strictures,  may  be  seen;  a  sawtooth  pattern  of  ureteral  involvement  has  been  reported.  Focal  or  diffuse  urinary  bladder wall thickening may be seen during the early stage of disease.  Marked  fibrosis  of  the  urinary  bladder  wall  results  in  a  small-capacity  bladder  referred  to  as  “thimble  bladder”. TB epididymo-orchitis and prostatitis may be seen in 70%–80% of patients with urinary tract involvement. Anti-TB chemotherapy is the standard of treatment of genitourinary tract TB.”
    Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation
    Krishna Prasad Shanbhogue et al.
    RadioGraphics 2023; 43(12):e230071
  • “Ascending infections lead to the development of mycetoma or “fungus balls” within the urinary tract that appear as non-enhancing filling defects on CT or MR urograms, with hyper-intensity on T2-weighted images (compared with the imaging appearance of renal parenchyma or bladder wall.  Multiple  microabscesses  and  tubulointerstitial  nephritis  result  from  hematogenous  spread  of  the  fungi.  While  Candida  microabscesses  appear  as  small  hypoattenuating  or  hypointense  lesions  within  bilateral  kidneys,  mucormycosis  manifests  as  solitary  or  multiple  unilateral  hypovascular  le-sions or abscesses. Mucormycosis shows marked proclivity for angioinvasion, leading to vessel thrombosis that results in infarction and hemorrhage with resultant high mortality rates in immunocompromised patients.”
    Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation
    Krishna Prasad Shanbhogue et al.
    RadioGraphics 2023; 43(12):e230071
  • “While  diffuse  XGP  is  easily  diagnosed  on  the  basis  of  a  constellation  of  findings  such  as  an  enlarged  kidney  with  a  contracted pelvis, dilated calyces (“bear’s paw” morphology), and staghorn calculi, focal and segmental types of XGP can be indistinguishable  from  tumors  on  imaging  studies.  Focal  XGP  may  appear  as  hypoattenuating  or  variably  enhancing masses or abscesses with associated perinephric or renal sinus  extension.”
    Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation
    Krishna Prasad Shanbhogue et al.
    RadioGraphics 2023; 43(12):e230071
  • “Immunoglobulin  G4  (IgG4)–related  disease  (IgG4-RD)  is  a  distinctive,  idiopathic,  multisystem  fibroinflammatory  dis-order with characteristic imaging, serologic (elevated serum IgG4 levels), and pathologic features. Renal involve-ment has been reported to occur in 7%–25% of patients with IgG4-RD,  with  the  majority  of  cases  being  incidentally  detected  at  imaging.  Common  clinical  manifestations  of  renal IgG4-RD include reduced kidney function, proteinuria, or hematuria. Plasma cell–rich tubulointerstitial nephritis with storiform fibrosis or “bird’s-eye fibrosis” and eosinophilia  comprise  the  most  common  histopathologic  findings  of  renal  IgG4-RD.”
    Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation
    Krishna Prasad Shanbhogue et al.
    RadioGraphics 2023; 43(12):e230071
  • “Diffuse  or  multifocal  hypoattenuating  masslike  lesions  showing  coalescence  and  affecting  bilateral  kidneys  are  typ-ical  imaging  findings .Characteristically,  the  nodules  are  isointense  on  T1-weighted  images,  are  hy-pointense  on  T2-weighted  images,  and  display  restricted  dif-fusion  and  progressive  contrast  enhancement.  Other  imaging  manifestations  of  renal  IgG4-RD  include  smooth  thickening of the renal pelvis, a renal sinus mass, and a peri-nephric mass . Synchronous changes of autoimmune pancreatitis  and  retroperitoneal  fibrosis,  if  present,  can  help  in narrowing the differential diagnosis. Most  patients  with  IgG4-RD  respond  exquisitely  to  corticosteroids. ”
    Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation
    Krishna Prasad Shanbhogue et al.
    RadioGraphics 2023; 43(12):e230071
  • Papillary necrosis
    - Ischemic necrosis of renal medulla and papillae:  vulnerable to ischemic necrosis
    - Risk factors: Diabetes mellitus, sickle cell anemia, analgesic abuse, chronic UTI, acute urinary obstruction
    - Compromised perfusion – vascular spasm, compression,  
    - +/- Hematuria, decreased renal function
    - Reversible ischemic change
    - Necrosis and sloughing of papillary tissue into the pelvicaliceal systems - soft tissue attenuation filling defect
    - Contrast material-filled papillary cavities 
    - Blunting of calyces 
  • Forniceal rupture 
    - Obstructing collecting system can decompress spontaneously by leakage of urine, typically from one or more caliceal fornices.
    - Caliceal fornix is the weakest point of the renal collecting system.
    - Extravasated contrast may surround the renal pelvis and proximal ureter on excretory phase CT urography.
    - The patient’s symptoms may improve abruptly due to decompression.
    - Forniceal rupture due to acute obstruction usually has no clinical significant if the urine is not infected.
  • Despite lithium being the most efficacious treatment for bipolar disorder, its use has been decreasing at least in part due to concerns about its potential to cause significant nephrotoxicity. Whilst the ability of lithium to cause nephrogenic diabetes insipidus is well established, its ability to cause chronic kidney disease is a much more vexing issue, with various studies suggesting both positive and negative causality. Despite these differences, the weight of evidence suggests that lithium has the potential to cause end stage kidney disease, albeit over a prolonged period. Davis, J.,
    Lithium and nephrotoxicity: a literature review of approaches to clinical management and risk stratification.  
    Desmond, M. & Berk, M.  
    BMC Nephrol 19, 305 (2018).
  • “In summary, the evidence attests to a small but definite risk of lithium-induced reduction in GFR and progression to CKD. Some studies indicate that the risk for CKD and ESRD is low while others suggest that long-term lithium treatment increases the risk for chronic nephropathy to a clinically relevant degree.”
    Lithium nephrotoxicity.  
    Azab AN, Shnaider A, Osher Y, et al.  
    Int J Bipolar Disord. 2015 Dec;3(1):28. 
  • "Malakoplakia is a rare granulomatous inflammatory disorder that predominantly affects the urinary tract; however, involvement of other organ systems such as the gastrointestinal (GI) tract, lungs, lymph nodes, and skin has also been reported. The bladder is the most likely portion of the genitourinary tract to be impacted by malakoplakia, followed by the kidneys . Renal lesions are usually bilateral and multifocal.”  
    Multimodal imaging appearance including cinematic rendering of renal malakoplakia in a patient with E. coli bacteremia  
    Nicholas E. Henlon, Elliot K. Fishman, Erin N. Gomez
    R a d i o l o g y Cas e R e p o r t s 1 8 ( 2 0 2 3 ) 7 0 9 – 7 1 4  
  •  “Previous literature has described the imaging findings of renal malakoplakia using imaging modalities including ultrasound, CT, and MRI. In prior literature, findings such as dif-  fusely increased renal parenchymal echogenicity, loss of corti- comedullary differentiation, nephromegaly, and renal masses on ultrasound have been associated with renal malakoplakia. In terms of CT findings, nephromegaly, mass-like lesions, abscesses, and inflammatory changes have been seen in renal malakoplakia patients. MRI findings of renal malakoplakia include nephromegaly, irregular renal contours, lack of cortico-medullarity differentiation, and intervening fibrous tissue and ill-defined parenchymal nodularity that is T1 and T2 hypointense .”  
    Multimodal imaging appearance including cinematic rendering of renal malakoplakia in a patient with E. coli bacteremia
    Nicholas E. Henlon, Elliot K. Fishman, Erin N. Gomez
    R a d i o l o g y Cas e R e p o r t s 1 8 ( 2 0 2 3 ) 7 0 9 – 7 1 4  
  • “One unique aspect of our case report is that cinematic and 3D renderings of the patient’s CT data were also generated as part of her imaging evaluation. To our knowledge, this is the first time that this technique has been used in a case of renal malakoplakia. Cinematic rendering incorporates a com- plex lighting model that traces the path of photons projected over materials within a specific volume to generate a 3D image. Use of cinematic rendering can aid in characterization of pathology due to use of photorealistic lighting, more accurate vascular mapping, and estimation of organ and lesion characteristics including texture and density.”  
    Multimodal imaging appearance including cinematic rendering of renal malakoplakia in a patient with E. coli bacteremia  
    Nicholas E. Henlon, Elliot K. Fishman, Erin N. Gomez
    R a d i o l o g y Cas e R e p o r t s 1 8 ( 2 0 2 3 ) 7 0 9 – 7 1 4 
  • “In conclusion, renal malakoplakia is a rare inflammatory disease that is characterized by macrophage dysfunction. Nonspecific imaging findings make diagnosis challenging, however, recognition of key imaging features and use of adjunct imaging modalities and postprocessing techniques including 3D and cinematic rendering of CT data may aid in accurate characterization of imaging findings and that may facilitate accurate diagnosis.”  
    Multimodal imaging appearance including cinematic rendering of renal malakoplakia in a patient with E. coli bacteremia  
    Nicholas E. Henlon, Elliot K. Fishman, Erin N. Gomez
    R a d i o l o g y Cas e R e p o r t s 1 8 ( 2 0 2 3 ) 7 0 9 – 7 1 4 
  • “Michaelis and Gutmann first described malakoplakia in 1902. The term malakoplakia is derived from the Greek words malakos, which means soft, and plakos, which means plague. The age at diagnosis ranges from 6 to 85 years, with an average age of 50 years at presentation. There is a female predominance, with a female to male ratio of 4:1. Malakoplakia can affect any organ system including the gastrointestinal system, bones, lungs, lymph nodes and skin, but the collecting system of the urinary tract is most frequently involved. The renal lesion is most often multifocal .”
    Renal malakoplakia presenting as a renal mass in a 55-year-old man: a case report  
    Maryam Abolhasani et al.
    Journal of Medical Case Reports 2012, 6:379
  • “Malakoplakia is an uncommon chronic inflammatory condition that has a gross and microscopic appearance resembling that of xanthogranulomatous pyelonephritis. It is characterized by distinctive Michaelis-Gutmann bodies. Malakoplakia can affect any organ system but genitourinary tract involvement is the most common, particularly iimmunocompromised individuals. Very rare cases have been reported to present as a unifocal lesion mimicking a renal tumor.”
    Renal malakoplakia presenting as a renal mass in a 55-year-old man: a case report  
    Maryam Abolhasani et al.
    Journal of Medical Case Reports 2012, 6:379
  • “Renal malakoplakia must be kept in mind for patients presenting with a renal mass and a history of long-term recurrent renal infections or renal failure. The large, rapidly growing nodules of malakoplakia may mimic renal cell carcinoma in imaging studies. In these cases, a true cut needle biopsy may help the correct diagnosis and prevent unnecessary surgery.”
    Renal malakoplakia presenting as a renal mass in a 55-year-old man: a case report  
    Maryam Abolhasani et al.
    Journal of Medical Case Reports 2012, 6:379
  • “In imaging studies, the appearance of the affected kidney ranges from that of a normal kidney to an enlarged, nonfunctioning kidney. Commonly, multiple poorly defined renal lesions enlarging the kidney, and often involving both kidneys, are present. The renal lesions can distort the pelvis and calices but seldom cause obstruction. Perirenal extension and renal vein thrombosis have been reported. Focal renal lesions are usually poorly defined and hypoechoic on ultrasound study. Parenchymal calcification is rare. A unifocal renal lesion is uncommon and can resemble a necrotic renal cell carcinoma. Differential diagnoses in radiologic studies include local abscess, granuloma, xanthogranulomatous pyelonephritis, lymphoma.”
    Renal malakoplakia presenting as a renal mass in a 55-year-old man: a case report  
    Maryam Abolhasani et al.
    Journal of Medical Case Reports 2012, 6:379
  • “The diagnosis of malakoplakia must be kept in mind for patients presenting with a renal mass and a history of long-term recurrent renal infections or renal failure [4]. Renal malakoplakia may mimic renal tumors and lead to unnecessary surgery. The patient in our report had renal malakoplakia but underwent a nephrectomy with the clinical diagnosis of a renal tumor. A nephrectomy can be a choice for unifocal malakoplakia, but the preoperative diagnosis of renal malakoplakia in appropriate clinical settings can prevent unnecessary surgery.”
    Renal malakoplakia presenting as a renal mass in a 55-year-old man: a case report  
    Maryam Abolhasani et al.
    Journal of Medical Case Reports 2012, 6:379
  • “The diagnosis of malakoplakia must be kept in mind for patients presenting with a renal mass and a history of long-term recurrent renal infections or renal failure. Renal malakoplakia may mimic renal tumors and lead to unnecessary surgery. The patient in our report had renal malakoplakia but underwent a nephrectomy with the clinical diagnosis of a renal tumor. A nephrectomy can be a choice for unifocal malakoplakia, but the preoperative diagnosis of renal malakoplakia in appropriate clinical settings can prevent unnecessary surgery.”
    Malacoplakia Presenting as a Solitary Renal Mass
    Aaron J. Wielenberg et al.
    AJR. 2004;183: 1703-1705
  • “The appearance of the affected kidney on im-aging studies ranges from that of a normal kidney   to   an   enlarged,   nonfunctioning   kidney. Commonly,  multiple  poorly  defined  renal  lesions  enlarging  the  kidney  and  often  involving both kidneys are present. The renal lesions candistort  the  pelvis  and  calices  but  seldom  cause obstruction.  Perinephric  extension  and  renal vein thrombosis have been reported. Focal renal  lesions  on  sonography  usually  are  poorly defined and hypoechoic. CT reflects the pathologic  range  of  renal  involvement  of  multifocal disease involving one or both kidneys. Most of-ten,  renal  enlargement  exists  with  poorly  de-fined,  variably  sized  solid  masses.  Perinephric extension  and  renal  vein  thrombosis  are  well. shown. Parenchymal calcification is rare [2, 6].A  unifocal  renal  lesion  is  uncommon  and  can resemble  a  necrotic  renal  cell  carcinoma,  as  in the  case  presented  here.  Neovascularity  is  generally  absent  but  has  been  reported  with  unifo-cal disease.”
    Malacoplakia Presenting as a Solitary Renal Mass
    Aaron J. Wielenberg et al.
    AJR. 2004;183: 1703-1705
  • Purpose To assess the clinical and imaging features of IgG4-RKD for understanding and diagnosis of this disease. Methods CT and MR images of 34 patients with IgG4-RKD were retrospectively analyzed by two radiologists in consensus.
    Results The serum IgG4 level was found being increased in all patients. Renal involvement was bilateral (24/34, 70.6%) or unilateral (10/34,29.4%), multiple (29/34, 85.3%) or solitary (5/34, 14.7%). The lesions were wedge-shaped or mass-like in the renal parenchyma, whereas diffusely decreased renal density was noted in 2 patients. All lesions showed progressive contrast enhancement. The 4 mass-like lesions were misdiagnosed as renal malignancy. In 15 patients with follow-up imaging examinations, the number and size of renal lesions decreased after oral hormone treatment. The serum IgG4 levels were significantly decreased after therapy in all patients.
    Conclusion IgG4-RKD has various imaging appearances. Although the mass-like appearance mimics renal malignancy in some patients, progressive contrast enhancement in the lesion with elevated serum IgG4 suggests IgG4-RKD.
    Clinical and imaging features of IgG4‐related kidney disease
    Jian Ling et al
    Abdominal Radiology (2020) 45:1915–1921
  • “In this study, only 2 patients had disease confined to the kidneys, while the remaining 32 patients had additionally extra-renal involvement, especially the pancreas (19/34, 55.9%) and biliary tree (18/34, 52.9%). The pancreas and biliary system have previously been reported to be most commonly affected in abdomen. The serum IgG4 level was increased in all patients, which was important for the diagnosis of IgG4-RKD.”
    Clinical and imaging features of IgG4‐related kidney disease
    Jian Ling et al
    Abdominal Radiology (2020) 45:1915–1921
  • "Renal involvement was frequent and variable appearance in our study. Similar to previous reports, we found multiple wedge-shaped or round lesions in the bilateral renal cortex or corticomedullary junction. The lesions had lower and progressive contrast enhancement than that of normal renal parenchyma in multiple phases, consistent with reports in the literature. This was thought to be related to the fibrotic tissue in the lesions.”
    Clinical and imaging features of IgG4‐related kidney disease
    Jian Ling et al
    Abdominal Radiology (2020) 45:1915–1921
  • “When IgG4-RKD presented as a solid mass, it has been misdiagnosed as lymphoma, urothelial carcinoma of the renal pelvis, or metastases leading unnecessary nephrectomy. In our study, 4 patients who presented with renal masses on CT were misdiagnosed as lymphoma and renal malignancy , urothelial carcinoma of the renal pelvis, pancreatic and renal malignancy. Reviewing the misdiagnosed cases in this study, the masses of IgG4-RKD showed progressive delayed enhancement with multiple organ involvement.”
    Clinical and imaging features of IgG4‐related kidney disease
    Jian Ling et al
    Abdominal Radiology (2020) 45:1915–1921
  • Imaging of Acute Pyelonephritis
    - Reniform enlargement
    - Perirenal stranding
    - Hydronephrosis possible due to bacterial neurotoxin
    - Typical CT findings: striations, wedge-shaped defects
    - DDx = Infarcts, infiltrating neoplasms
  • Intrarenal Abscess: CT Findings
    - Fluid containing areas in renal parenchyma
    - Usually co-exists with pyelonephritis findings
    - CT more sensitive than US
    - Debris in fluid may be detectable with US only
    - < 3cm usually not drained
  • Granulomatous Renal Infections
    - Tuberculosis
    - XGP
    - Malacoplakia
    - Fungal infections
  • Renal Tb - Imaging
    - Primary is invisible
    - Usually unilateral
    - Abscess
    - Does not respect fascial planes
    - Urothelial ulcerations
    - Scarring & fibrosis
    - Calcifications
  • Cystitis: Diagnostic Imaging Clues
    - Gas = EC
    - Mural Calcifications = Schistosomiasis
    - Chronic UTIs + focal lesions = CC
    - Alkaline urine + Ca++ = AEC
    - Pear shaped bladder = CG
    - Contracted bladder + chemotherapy = Cytoxan
    - Eosinophilia = EC
  • Key Points: Imaging of UTI per Ron Zagoria
    - Diagnosis requires action: Abscess, Emphysematous pyelo, pyonephrosis, Fournier’s
    - XGP: Classic triad, not hydronephrosis
    - Schistosomiasis: Consider SCC
    - Rapidly changing urethral sx: Think SCC
    - Look for gas where it shouldn’t be!
  • “The most common abdominal manifestation of ECD is retroperitoneal xanthogranulomatosis, with involvement of the kidneys, ureters, and aorta. Perirenal and periureteral manifestations of ECD include a thick rind-like soft-tissue lesion encasing the renal parenchyma and ureters leading to obstruction. This perirenal soft-tissue infiltration has a characteristic, so-called hairy kidney appearance, which is pathognomonic for ECD.”


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, 
Inflammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “ECD is a rare multisystem non–Langerhans cell histiocytotic disorder primarily affecting middle-aged to older adults, with a slight male predominance. Histologically, ECD shows focal fibrosis with foamy histiocyte infiltration. The histiocyte cells are positive for cluster of differentiation (CD) 68 and negative for S-100, CD1a, or Birbeck granules, which differentiates ECD from Langerhans type histiocytosis.”


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, In ammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “FDG PET allows accurate evaluation of the extent of the disease; it also helps in assessing the degree of visceral and vascular involvement. As with all XG processes, ECD exhibits GLUT receptors, and FDG uptake is seen in the organs affected. Retroperitoneal xanthogranulomatosis usually exhibits intense FDG avidity.”


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, In ammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “Another important retroperitoneal structure involved is the aorta, which presents with circumferential soft-tissue-like sheathing, giving a so-called coated aorta appearance. The infiltration may extend into the branching vessels, such as the mesenteric and renal arteries.”


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, In ammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “Xanthogranulomatous processes are un- common. However, they should be considered when an aggressive process is present on abdominal imaging. Although XG processes are nonspecific, recognizing features of XG processes may have a significant impact on patient management, surgical planning, and patient morbidity. Imaging also plays a significant role in assessing disease extension and commonly occurring associated complications. Knowledge of the histopathologic behavior of these processes may aid in consideration of xanthogranulomatous entities in a differential diagnosis.”


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, Inflammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • ”XG pyelonephritis is an unusual variant of chronic pyelonephritis or recurrent bacterial tract infections. It occurs in the setting of chronic obstruction from an infected renal stone and altered immune response. These infections produce a chronic granulomatous 
inflammatory response and eventual destruction of the renal parenchyma, with the renal parenchyma eventually being replaced by lipid-laden (foamy) macrophages.” 


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, Inflammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “Typically, a large staghorn calculus and hydronephrosis are seen. Other associations with XG pyelonephritis include ureteropelvic junction obstruction, ureteropelvic duplication, bladder tumor, chronic interstitial nephritis, and calyceal stones.”


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, Inflammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “XG pyelonephritis typically presents in middle-aged women with a history of recur- rent urinary tract infections, diabetes mellitus, or obstructing renal calculi. Cases in children and in the elderly are also reported. The patient may present with nonspecific complaints such as malaise, fatigue, lethargy, recurrent low-grade fever, and flank pain.”

    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, Inflammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “Clinically, patients may present with a palpa- ble abdominal mass, urinary tract infections, or fistulous tracts. Laboratory studies often show leukocytosis, anemia, elevated C-reactive protein, and erythrocyte sedimentation rate. Positive urine cultures with Proteus mirabillis and Escherichia coli are most frequently seen with XG pyelonephritis, although other pathogens may be found.”

    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, Inflammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “Contrast-enhanced CT shows low-attenuation blown-out calyces replacing the renal parenchyma and cortical thinning, representing the classic “bear paw sign”. These blown-out calyces either signify dilated calyces or renal parenchyma filled with pus, debris, or hemorrhage.” 


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, Inflammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “Peripheral enhancement of the masses is also seen. The remainder of the kidney often shows nonenhancement or lack of excretion, indicating a nonfunctioning kidney. A large staghorn calculus with contraction of the renal pelvis can be seen. Associated hypoattenuation is often seen in the renal pelvis mimicking hydronephrosis, but in most cases this region of hypoattenuation rep- resents an extensive inflammatory process.” 


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, Inflammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “Surrounding perinephric inflammatory changes are common with extrarenal exten- sion. A high rate of complications is reported with diffuse XG pyelonephritis, including perforation with abscess formation involving the spleen, paraspinal muscles, or psoas muscles. Fistula tracts are also common, with case reports of renocutaneous, renocolic, or nephrobronchial fistula tracts.” 


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, Inflammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • “Xanthogranulomatous (XG) processes are rare inflammatory conditions with the characteristic pathologic feature of lipid-laden macrophages or histiocyte cells. Imaging findings are nonspecific and can simulate aggressive neoplastic processes. XG processes can be caused by infection, inflammation, histolytic process, or an inherited lysosomal disorder. XG infectious processes are mainly seen in cholecystitis and pyelonephritis, but several other organs can also be involved. Histiocytic processes can be divided into Langerhans and non–Langerhans cell histiocytosis. The non–Langerhans cell histiocytosis entities include Erdheim-Chester disease, Rosai-Dorfman disease, juvenile xanthogranuloma, and he- mophagocytic lymphohistiocytosis. The inherited lysosomal disorders resulting in XG processes include Nieman-Pick, Gaucher, and other lysosomal storage disorders.” 


    Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, Inflammatory, and Proliferative Responses 
Kelsey S. Bourm et al.
AJR 2017; 208:475–484
  • • Hemorrhagic bacterial nephritis: wedge- shaped area of increased attenuation related to an intraparenchymal hemorrhage 

    • Focal pyelonephritis: focal ill-defined infection with a masslike appearance that can mimic a neoplasm.

    • Hematogenousseeding:multiple,bilateraperipheral round low-attenuation lesions in the setting of systemic staphylococcal or streptococcal infection. 

    • Emphysematous pyelonephritis: gas within the renal parenchyma.”


    Acute Urinary Tract Disorders 
Goel RH et al.
Radiol Clin N Am 53 (2015) 1273–1292
  • “Emphysematous pyelonephritis and pyelitis are also diagnoses seen primarily in diabetic patients. About 90% of patients with emphysematous pyelonephritis have diabetes and present with costovertebral tenderness, fever, and rarely crepitus in the flank region or scrotum. The most com- mon causative organism is E coli, followed by Klebsiella pneumoniae. About 50% of patients have bacteremia. CT, the imaging study of choice for emphysematous pyelonephritis, demonstrates gas within the renal parenchyma, asymmetric renal enhancement with delayed contrast excretion, and focal regions of necrosis or abscess.”

    Acute Urinary Tract Disorders 
Goel RH et al.
Radiol Clin N Am 53 (2015) 1273–1292
  • “Gas in the bladder lumen may be from a gas- forming urinary tract infection (typically E coli), a bowel-bladder fistula, or recent instrumentation. Emphysematous cystitis involves gas within the bladder wall and is most commonly seen in middle-aged diabetic women . In contrast to the high mortality rate and surgical management of emphysematous pyelonephritis, 90% of patients are treated with medical management, and the mortality rate is only 7%.”


    Acute Urinary Tract Disorders 
Goel RH et al.
Radiol Clin N Am 53 (2015) 1273–1292
  • “In the setting of relevant risk factors (myocardial infarction, malignancy, aortic aneurysm, and cardiac valvular disease), CT imaging with contrast should be performed when there is an enlarged kidney with surrounding perinephric edema of unknown cause on an initial unenhanced CT. The most common cause for renal infarction is thromboembolism from a cardiac source. Although nonspecific, markedly elevated serum lactate dehydrogenase levels, a serum marker for cell necrosis, is helpful in suggesting the diagnosis.”

    Acute Urinary Tract Disorders 
Goel RH et al.
Radiol Clin N Am 53 (2015) 1273–1292
  • “Acute cortical necrosis is a rare variant (2% of acute renal failure) of global ischemia related to either diffuse vasospasm or injury to the distal arcuate arteries (acute tubular necrosis) in which there is a relative decrease in peripheral cortical enhancement, with sparing of the medulla (F. More than 50% of cases are associated with obstetric-related hemorrhage, most commonly placental abruption. There is bilateral kidney damage due to the systemic causes, resulting in high mortality (>50%).”


    Acute Urinary Tract Disorders 
Goel RH et al.
Radiol Clin N Am 53 (2015) 1273–1292
  • Genitourinary TB : Facts
    - The GU tract is affected by TB in 15-20% of patients with extrapulmonary involvement
    - The interval between initial pulmonary infection and the manifestations of genitourinary disease varies from 5 to 40 years
    - Symptoms are often nonspecific with increased frequency, dysuria and hematuria
    - 20% of patients with GU TB have a negative result at skin testing
  • Genitourinary TB : CT Findings
    - Papillary necrosis
    - Renal calcifications may be amorphous, granular, curvlinear or globular in appearance
    - Fibrosis or stricture may occur
    - Parenchymal scarring with non functioning kidney may occur ( “putty kidney”)
    - Ureter or bladder involvement always seen with renal involvement
  • “ The diagnosis of renal tuberculosis should be considered when a patient has recurrent urinary tract infections that do not fully resolve after conventional antibiotic therapy and when fine urothelial calcifications and caliceal dilatation are seen at imaging.”
    Genitourinary Tuberculosis
    Wong A et al
    RadioGraphics 2012; 32:839-844
  • Pyelonephritis

    - Mimics renal infarcts
    - Mimics renal vein thrombosis
    - Mimics obstruction with striated nephrogram
    - Mimics lymphoma
  • Acute Abdominal Pain

    Siewert et al, AJR 1997;168:173-178

    - 91 patients with acute abdomen
    - CT compared with clinical evaluation
    - CT was superior to clinical evaluation - Sensitivity: CT (90%), Clinical Eval (76%)
    - CT changed management in 25/91 patients
  • Acute Pyelonephritis: CT Findings

    - Enlarged, swollen kidney
    - Perinephric stranding
    - Delay in contrast excretion
    - Loss of corticomedullary differentiation
    - Striated nephrogram: Striations result from stasis of contrast within edematous tubules that demonstrate increasing attenuation overtime
    - Focal pyelonephritis can mimic a mass
  • Erdheim-Chester Disease: Facts

    - Renal and perirenal involvement in up to 29% of cases
    - May encase the thoracic or abdominal aorta (looks like retroperitoneal fibrosis)
    - Cardiac infiltration may be endocardial, myocardial or pericardial
  • Erdheim-Chester Disease: Facts

    - Rare form of non-Langerhans cell histiocytosis
    - Characterized by tissue infiltration by foamy histiocytes
    - Usually in patients over age 40
    - Can be life threatening
  • Perinephric Mass: Differential Dx

    - Proliferative diseases
    - Extramedullary hematopoiesis
    - Retroperitoneal fibrosis
    - Rosai-Dorfman disease
    - Erdheim-Chester disease
  • Perinephric Mass: Differential Dx

    - Fluid
    - Hematoma
    - Urinoma
    - Abscess
    - Pancreatic pseudocyst
  • Papillary Necrosis: Etiologies

    - Diabetes
    - Analgesic abuse
    - Sickle cell disease
    - Renal vein thrombosis
    - Obstructive uropathy
  • "The attenuation coefficient of a cystic renal lesion increased by no more than 10H among the unenhanced, corticomedullary, and parenchymal phase scans."

    Analysis of Changes in Attenuation of Proven Renal Cysts on Different Scanning Phases of Triphasic MDCT
    Chung EP et al.
    AJR 2004; 182:405-410
  • "This study shows that cystic lesions typically reveal a change in attenuation of less than 10HU between the scanning phases of a triphasic MDCT, affirming Bosniaks initial assertion that 10HU is a reasonable cutoff for determining enhancement in renal lesions."
  • "This study shows that cystic lesions typically reveal a change in attenuation of less than 10HU between the scanning phases of a triphasic MDCT, affirming Bosniaks initial assertion that 10HU is a reasonable cutoff for determining enhancement in renal lesions."

    Analysis of Changes in Attenuation of Proven Renal Cysts on Different Scanning Phases of Triphasic MDCT
    Chung EP et al.
    AJR 2004; 182:405-410

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