CT Urography for the Diagnosis of Medullary Sponge Kidney

Abstract

Background: Medullary sponge kidney (MSK) is characterized by malformation of the terminal collecting ducts and is associated with an increased risk of nephrolithiasis, nephrocalcinosis, urinary tract infections, renal acidification defects, and reduced bone density. It has been historically diagnosed with intravenous pyelography (IVP), which is falling out of favor as an imaging modality. CT urography (CTU) performed with multidetector CT (MDCT) has been shown to create images of the renal collecting system with similar detail as IVP; however, its utility in diagnosing MSK has not been defined. Case Report: We present the first 15 patients with recurrent symptomatic nephrolithiasis who were evaluated in our renal stone clinic with CTU. Four patients were diagnosed with MSK after visualization of the characteristic radiologic findings. Discussion: CTU effectively demonstrates the characteristic radiologic findings of MSK including collecting tubule dilatation, medullary nephrocalcinosis, nephrolithiasis, and medullary cysts. Dose reduction protocols can reduce radiation exposure below that associated with conventional IVP. We propose CTU be considered for the diagnosis of MSK.

Biopsy Proven Medullary Sponge Kidney: Clinical Findings, Histopathology, and Role of Osteogenesis in Stone and Plaque Formation

“…The characteristic shape of papillae involved with MSK permits differentiation from all other types of stone disease: rounded contours, enlargement, and a puffy, inflated, soft, and billowy appearance. That this surgical appearance is diagnostic of MSK, whether diffuse or segmental supports the idea that clinical diagnosis of MSK must rely on direct visualization at the time of surgery, or perhaps intravenous pyelography or CT urography (Maw et al, ; Koraishy et al, ), but not on other forms of radiography.…”

CT Urography for Diagnosis of Upper Urinary Tract Urothelial Carcinoma: Are Both Nephrographic and Excretory Phases Necessary?

“…Nephrographic phase CT has several advantages over split-bolus CTU: shorter examina-tion time, better evaluation of solid organs, and ability to potentially reveal significant urinary tract stones without unenhanced CT. On the other hand, excretory phase CT can reveal abnormalities of the urinary tract that may cause hematuria such as papillary necrosis, renal tubular ectasia, and calyceal diverticulum [27][28][29]. Future studies are needed to compare the diagnostic performance of the nephrographic phase, excretory phase, and combination of the two phases for identifying the cause of hematuria other than upper tract urothelial carcinoma.…”

Renal stone disease

“…However, CT urography seems to have similar diagnostic accuracy in this setting. 9 Computed tomography (CT-KUB): an unenhanced (noncontrast) CT scan is now the gold standard investigation in most hospitals in the diagnosis of urinary tract stones in an emergency. The CT-KUB is reported to have a sensitivity of 97% and a specificity of 96%.…”