Congenital and acquired renal diseases that can produce renal insufficiency during the neonatal period may be classified according to their ultrasonographic (US) characteristics: increased parenchymal echogenicity (renal parenchymal diseases, angiotensin-converting enzyme inhibitor fetopathy, cortical necrosis), cystic disease (glomerulocystic kidney disease, autosomal recessive polycystic renal disease, multicystic dysplastic kidney, cystic renal dysplasia), obstructive uropathies (ureteropelvic junction obstruction, posterior urethral valves), infections (candidal infections and bezoars), and renal agenesis. High-resolution sector and linear-array transducers allow characterization of the underlying pathologic conditions in many cases. Findings of renal parenchymal disease will vary at Doppler US and, during the acute phase, diastolic flow can be decreased, absent, or reversed. In patients with glomerulocystic kidney disease, US shows bilaterally enlarged kidneys with diffusely increased echogenicity and retention of a reniform contour, loss of corticomedullary differentiation, and cortical cysts. Obstruction of the ureteropelvic junction, the most common cause of hydronephrosis in neonates, can be seen at US as a dilated renal pelvis with dilated and communicating calices, lack of dilatation in the distal portion of the ureter, changes of renal dysplasia with increased echogenicity of the renal parenchyma, and parenchymal cysts, depending on the severity and duration of the obstruction. High-resolution US provides improved characterization of the renal parenchyma and more precise description of renal architecture.

The most common renal lesions of tuberous sclerosis complex, an autosomal-dominant syndrome resulting from losses of TSC1 (9q34) or TSC2 (16p13.3), are renal cysts and angiomyolipomas. Epithelial neoplasms are less common. The TSC2 gene lies adjacent to PKD1, the major gene responsible for autosomal-dominant polycystic kidney disease. Recently, a deletion mutation disrupting both TSC2 and PKD1 has been described in young children with tuberous sclerosis complex with severe renal cystic disease. This disease has been termed the TSC2/PKD1 contiguous gene syndrome. We describe the lesions in the resected kidneys of two adults with TSC2/PDK1 contiguous gene syndrome, at the time of the nephrectomies: a 31-year-old man and his 44-year-old mother. The four kidneys were enlarged reniform masses composed of cysts lined by flattened, cuboidal, or, infrequently, large deeply eosinophilic epithelial cells. The kidneys also contained numerous classic angiomyolipomas and rare intraglomerular microlesions. In the son the largest tumor was a monotypic epithelioid angiomyolipoma. In the wall of his left renal pelvis there was a plaque-shaped, HMB-45-positive localized lesion of lymphangioleiomyomatosis. This is the first description of the renal lesions in adults with genetically confirmed TSC2/PDK1 contiguous gene syndrome. The pathologic findings highlight the importance of thorough sampling for histology in polycystic kidney diseases and indicate that the observation of an angiomyolipoma in biopsy material from patients with enlarged cystic kidneys should suggest the diagnosis of TSC2/PKD1 contiguous gene syndrome, even in cases without ultrasonographic and macroscopic evidence of angiomyolipoma.

The urothelium is a target tissue for carcinogens that lead to the development of transitional cell carcinomas (TCCs), both synchronous and metachronous. Although there are pathologic and imaging features common to transitional cell tumors occurring anywhere in the genitourinary tract, certain findings are more typical of tumors of the renal pelvis, ureter, or urinary bladder. A slightly irregular, fixed mass arising from any urothelial surface is characteristic of TCC. Although such masses are usually confined to the collecting system lumina, larger lesions that arise in the renal pelvis may extend into the renal parenchyma, typically in an infiltrative pattern that preserves the reniform shape. In contrast to the rapidly developing mural edema associated with obstructing calculi, the relatively slow growth of ureteral TCC allows for gradual expansion of the ureteral lumen around the tumor and is less likely to produce acute renal colic. Focal wall thickening, either eccentric or circumferential, may also be a manifestation of TCC of the ureter or, less commonly, other portions of the urinary tract. The urinary bladder is the most common site of TCC; lesions are generally confined to the lumen and typically do not extend beyond the bladder wall until quite large.

In 5 patients with invasive renal pelvic cancer, we evaluated the imaging features of drip infusion pyelography (DIP), retrograde pyelography (RP), ultrasonography (USG), computerized tomography (CT), magnetic resonance imaging (MRI) and renal angiography (RAG). The different features of high diagnostic value were as follows. DIP revealed no visualization with enlargement and reniform outline. RP revealed irregular, serrated filling defect of the pelvis with destruction of the involved calyces and infundibula. USG revealed loss of normal parenchymal architecture with amputation of the central echo complex due to echogenic mass. CT revealed widened renal parenchyma and the involved parenchymal segment, which was replaced by tumor mass with inhomogeneous density and minimal enhancement. MRI denoted renal vein thrombus. RAG revealed, besides the fine neovascularity with tumor blush, hypovascularity in the involved area. In addition to these features, we believe that in particular, RP, USG, CT and RAG are useful tools for patients with non-functioning kidney.

Ultrasound diagnosis of horseshoe kidneys depends on the demonstration of an isthmus or band of renal tissue across the midline of abdomen connecting the lower poles of the kidneys. In a number of cases this band of renal tissue may evade ultrasonic detection. In a series of 11 patients with horseshoe kidneys, sonographic detection of renal isthmus was achieved in seven patients, but in all 11 cases there was demonstrable alteration of renal outlines. Instead of normal reniform shape, the kidneys appeared "inverted pyriform" or "inverted triangular". Detection of such an altered renal outline should raise suspicion of horseshoe kidney.

Epidermoid carcinoma of the kidney is a rare malignant tumor, characterized by high invasiveness, poor prognosis, and the association of renal stone and renal infection. Very little reports about its sonographic appearance were mentioned in the literature. We present a case of epidermoid carcinoma of the kidney. Its ultrasonography showed a heterogeneous renal mass with perirenal and pararenal invasion, destruction of the renal pelvis, and preservation of enlarged reniform outline. Although this tumor should be differentiated with renal cell carcinoma, transitional cell carcinoma, renal metastatic tumor, renal lymphoma, renal infarction, focal bacterial nephritis, and xanthogranulomatous pyelonephritis etc., we think we should put epidermoid carcinoma of kidney into consideration when a renal tumor mass presents with perirenal and pararenal invasion, destruction of the renal pelvis, and preservation of enlarged reniform outline in sonography, and hypovascularity in angiographic study.

The CT and sonographic findings in 23 cases of renal lesions in which the abnormality was infiltrative, as opposed to expansile, were analyzed (invasive transitional cell carcinoma [seven], renal lymphoma [six], metastasis to the kidney [three], acute bacterial nephritis [three], mesoblastic nephroma [two], squamous cell carcinoma of the renal pelvis [one], and renal cell carcinoma [one]). CT scans were evaluated for shape and density of the mass, pelvocaliceal displacement, effect on the renal sinus fat, and the presence of perirenal involvement. Sonograms were evaluated for the shape and echogenicity of the mass and for the effect on the renal sinus echoes. Findings of infiltrative growth included poorly defined margins of the mass; trapped, nondisplaced infundibulae; and calices with occasional calicectasis, diminished contrast enhancement, occasional nephrographic striations, replacement of central sinus fat, loss of central sinus echoes, and variable renal parenchymal echogenicity. The reniform shape was usually preserved and was present in 19 of 20 cases with CT and 13 of 15 cases with sonograms. These observations indicate that analyses of the margins, architecture, and effects on the collecting system and renal sinus by the mass are helpful in the diagnosis of those diseases that characteristically infiltrate the kidney.

A clinical-radiologic-pathologic correlation study was performed in 18 (17 female) patients with xanthogranulomatous pyelonephritis (XGP) with CT scans available for analysis. Presenting signs and symptoms included pain (66%), urinary frequency (66%), dysuria (66%), nocturia (66%), palpable mass (56%), leukocytosis (50%), and fever (50%). The duration of symptoms was usually relatively short (less than 6 months), considering the extent of the pathologic process. In 14 patients, the disease was diffuse; the kidney was enlarged with preservation of the reniform outline in 13. The renal pelvis, lined with sheets of lipid-laden macrophages and surrounded by a marked fibrotic reaction, was contracted in 11 and contained pelvic calculi in 12. The parenchyma was replaced by multiple, rounded, low-density areas on CT that corresponded to dilated calices and/or inflammatory tissue. These areas had enhancing rims (10 cases) that corresponded to preserved, compressed normal parenchyma and/or inflammatory tissue. There was CT identification of unsuspected extension through the renal capsule with involvement of the perirenal space in 11 patients, the pararenal spaces in 13, and the psoas muscle in six. The pararenal space and the psoas muscle were often extensively involved with minimal perirenal disease in six patients, a reflection of chronic indolent infection. There were four cases of focal XGP that appeared on CT as low-density mass lesions with wall enhancement surrounding dilated, stone-filled calices or as focal masses occupying one pole of a duplication. Extensive pararenal disease was present in two of the four cases of focal XGP. The preoperative diagnosis of XGP was suspected in only 44% of cases. It is concluded that CT should play a role in diagnosis and preoperative planning to demonstrate the extent of extrarenal disease that is poorly depicted by other means.

We present 8 patients with transitional cell carcinoma of the kidney who underwent preoperative computerized tomographic examination of the lesions. The computerized tomographic findings are discussed and are correlated with the conventional radiographic appearance. The tumor presents on computerized tomographic examination as a solid mass in the renal pelvis and/or in a ballooned calix, with displacement and compression of the renal sinus fat. It shows attenuation values of 8 to 20H and enhances minimally after intravenous injection of iodinated contrast material. Trapping of contrast material in curvilinear caliceal spaces or in compressed collecting ducts around the periphery of the tumor results in crust-like rims of contrast density tightly and persistently encircling portions of the tumor. Retention of contrast material in obstructed tubules results in accentuated delayed enhancement of the renal parenchyma surrounding the larger lesions. A striated parenchymal pattern, secondary to uneven collecting duct obstruction, also may be seen on delayed views. The reniform contour of the kidney usually is preserved even in the presence of larger neoplasms.

Three related puppies with abdominal distention caused by nephromegaly and hepatomegaly had gross and histologic lesions in the kidney and liver similar to polycystic disease of children. Both kidneys were enlarged and reniform, and contained multiple fusiform or cylindrical cysts lined by cuboidal epithelium radiating through the cortex and medulla. Various amounts of connective tissue surrounded the cysts. The glomeruli and renal pelvis were normal. Histologically, the liver was diffusely subdivided by fibrous connective tissue extending from one portal triad to another. Within the connective tissue, there was proliferation of biliary epithelium, giving the gross appearance of multiple cysts within normal hepatic parenchyma.