GENITOURINARY IMAGING: Collecting System, Ureter, Bladder
Case Author: Matthew S. Hartman, MD, Allegheny General Hospital
History
45-year-old diabetic woman with microscopic hematuria
Imaging Findings
Coronal volume-rendered reconstruction of excretory phase CT urogram (A) shows bilateral irregular calyces with contrast-filled clefts. Coronal reformatted image (B) shows contrast material from the collecting system filling a cavity in the papilla (arrow). Axial CT image (C) shows contrast material (arrow) in a cavity in the papilla. Coronal CT image (D) shows a filling defect (arrow) in an upper calyx.
Diagnosis
Papillary Necrosis
Teaching Points
Detection of papillary necrosis should prompt investigation and correction of the underlying cause of ischemia. Failure to do so can result in continued ischemic injury leading to renal scarring.
Diabetes mellitus, analgesic nephropathy, sickle cell disease, and pyelonephritis are the common conditions that cause papillary necrosis by compromising the blood supply to the renal papillae.
Features of papillary necrosis at CT urography include contrast-filled clefts in the renal medulla, filling defects surrounded by rings of excreted contrast medium, and medullary calcifications. An early sign of medullary ischemia is small areas of diminished enhancement at the tip of the medullary pyramids, best seen in the nephrographic phase.
Calyceal diverticulum refers to a urine-containing cystic cavity in the renal parenchyma. The diverticulum is lined by transitional epithelium, and when it communicates with the collecting system, it does so via a narrow isthmus. A calyceal diverticulum can become symptomatic owing to infection and stone formation, both of which are precipitated by urinary stasis.
Medullary sponge kidney is a developmental abnormality characterized by cystic dilation of the renal collecting tubules. Changes range from mild dilation of the collecting tubules (often called renal tubular ectasia) to gross deformities with multiple cystlike cavities of various sizes. It is usually a benign disorder and often is asymptomatic. Urinary calculi and urinary tract infection are the most common complications..
Suggested Readings
Jung DC, Kim SH, Jung SI, Hwang SI, Kim SH. Renal papillary necrosis: review and comparison of findings at multi-detector row CT and intravenous urography. RadioGraphics 2006; 26:1827–1836
Lang EK, Macchia RJ, Thomas R, et al. Detection of medullary and papillary necrosis at an early stage by multiphasic helical computerized tomography. J Urol 2003; 170:94–98
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