Tumors of the Kidney, Bladder, Ureters, and Renal Pelvis

Definition

Cancers of the kidney are a heterogeneous group of neoplasms, the majority of which are of epithelial origin and malignant. Renal cell carcinoma, classically referred to as clear cell carcinoma or hypernephroma, is not a single malignancy. Rather, renal cell carcinoma comprises a group of distinguishable entities ( Table 182-1 ), each with a strong relationship between its morphologic and genetic features. The metastatic potential depends on the histologic subtype and ranges from the most virulent conventional clear cell carcinomas (65% of total tumors but accounting for 90% of the metastases), to the more indolent papillary and chromophobe carcinomas (25% of the total but only 10% of the metastases), and to the benign oncocytomas (10% of all tumors).

Epidemiology

Over 75,000 new tumors of the kidney and renal pelvis are diagnosed in the United States annually, and they result in approximately 14,000 deaths each year. These cancers represent the sixth most common form of cancer in men and the ninth most common in women. The increase in incidence of renal cell cancers may be in part related to early detection as a consequence of computed tomography (CT) and magnetic resonance imaging (MRI) of the abdomen for other medical conditions. The ratio of males to females is approximately 2 : 1 to 3 : 1, and the incidence is highest in Black Americans and lowest in Asians and Pacific Islanders. The mean age at diagnosis is in the sixth to seventh decade of life. Aside from genetic predisposition, risk factors associated with renal cell carcinoma include cigarette smoking, obesity, hypertension, and the use of diuretics. Obese persons have an increased risk for renal cell carcinoma, and the risk rises with increasing body mass index. The elevated risk associated with diuretic use is difficult to distinguish from the increased risk associated with hypertension. Renal cell carcinoma is more prevalent in patients with pre-existing renal injury, such as polycystic kidney disease ( Chapter 112 ), horseshoe kidney ( Chapter 113 ), and chronic renal failure requiring hemodialysis ( Chapters 116 and 117 ).

Pathobiology

Clinical Manifestations

The majority of patients are asymptomatic at presentation, with about 50% of tumors detected by an abdominal ultrasound, a CT scan, or an MRI obtained for unrelated medical reasons. The next most common presentation is with asymptomatic hematuria, often microscopic. The classic presenting triad of hematuria, a palpable mass, and pain is now unusual, and less than 5% of patients have a palpable mass at presentation. The more common manifesting symptoms are anemia, weight loss, malaise, and anorexia ( Table 182-3 ). Patients who present with renal cell carcinoma frequently have associated paraneoplastic syndromes ( Chapter 164 ). Hypercalcemia ( Chapter 227 ) is observed in approximately 20% of patients and can be due to the secretion of parathyroid hormone, parathyroid hormone–like peptide, and interleukin-6 (IL-6), which stimulate osteoclastic bone resorption. Other associated syndromes include hypertension, erythrocytosis (from ectopic erythropoietin production), and the rare Stauffer syndrome, which is liver dysfunction without hepatic metastases and which resolves after surgical resection of the tumor.

Diagnosis

Ultrasonography, CT, and MRI can help distinguish benign from malignant lesions. Ultrasound can distinguish small simple cysts from solid lesions. For other renal cystic lesions, CT or MRI can define three categories: likely benign lesions that require no follow-up; lesions that are usually benign (generally smooth wall of no more than 3 mm with enhancing septa) but require repeat imaging at 6 months, 12 months, and then annually for 5 years; or thicker-walled or irregularly enhancing lesions that require biopsy.

CT is the most reliable method for evaluating solid lesions. The preferred CT scan for renal masses can be divided into four phases, including the precontrast images, the arterial phase (~25 seconds after injection), the nephrographic phase (~90 seconds into the injection), and the excretory phase. The most important phases for imaging renal tumors are the precontrast and nephrographic images because renal lesions appear low in density in contrast to the uniformly enhanced renal parenchyma. The arterial phase is helpful for identifying renal arteries and small hypervascular masses. The excretory phase aids in assessing the collecting system and the renal pelvis. Lack of enhancement is consistent with a hemorrhagic or inflammatory cyst that can mimic a solid lesion. Macroscopic fat in a solid renal mass suggests an angiomyolipoma.

The complete evaluation for patients with suspected renal cell carcinoma should include a complete blood count, a chemistry profile, and a CT scan of the chest, abdomen, and pelvis. CT scan is also helpful for detecting regional metastases and for indicating when partial nephrectomy is feasible. MRI is useful for imaging tumors in patients who have poor renal function and in whom intravenous contrast may be contraindicated. MRI is also helpful for delineating any thrombi that may be extending into the renal vein or inferior vena cava, and magnetic resonance angiography can determine the number and location of renal arteries in patients who are candidates for partial nephrectomy. Once the evaluation is complete, the clinical stage is assessed using the Tumor, Node, Metastasis (TNM) system ( Table 182-4 ). A bone scan is indicated for patients with clinically advanced disease, hypercalcemia, bone pain, and/or an elevated alkaline phosphatase level.

Treatment