Renal cell adenocarcinoma (hypernephroma) is about twice as frequent in males as in females. It occurs with about equal frequency in both kidneys. About 90% of cases occur after age 40, although more than 30 cases have been reported in children. About 80% of renal cell carcinomas are located in either the upper or the lower poles of the kidney.

Clinical findings. In renal cell adenocarcinoma, symptoms and urinary findings vary according to the location, size, and aggressiveness of the tumor. Renal carcinoma often causes hematuria (as does bladder carcinoma). Painless gross hematuria is the initial symptom in about 40% of patients and occurs with other symptoms in additional cases. These episodes are often intermittent and may be misdiagnosed as urinary tract calculus or infection. Flank pain is present in about 40% of patients, and about one third have a significant degree of weight loss. A mass is noticeable to the patient in about 10%–15% of cases and is palpable by the physician in about 50% of cases. In addition, hypernephroma, on occasion, is a well-recognized cause of fever of unknown origin. It has rarely but repeatedly been associated with secondary polycythemia (about 3% of patients), although a large minority have anemia and the majority do not show hemoglobin abnormality. About 20% of patients have hypertension (range, 4%–38%). About 10% (range, 4%–28%) have no clinical symptoms suggestive of hypernephroma, and the tumor is discovered on intravenous pyelogram (IVP) performed for some other reason.

Laboratory findings. Hematuria, either gross or microscopic, is the most frequent abnormality, being detected at some time in about 60% of patients (range, 28%–80%). Unfortunately, most publications either do not differentiate between gross and microscopic hematuria or record gross hematuria only. In 38 patients with renal cell adenocarcinoma seen in my area, 39% had gross hematuria and an additional 27% had microscopic hematuria. Proteinuria may be present but is less frequent. About 30% of patients have a completely normal urinalysis on admission. The IVP is the most useful screening test for renal cell carcinoma and, if carefully done, will also detect many cases of carcinoma in the renal pelvis and ureters. Other procedures, such as kidney scanning or computerized tomography (CT), are also useful.

Other procedures. Once a space-occupying lesion is identified in the kidney, the question arises as to its nature. B-mode ultrasound, CT, and drip infusion tomography seem to be excellent methods of distinguishing a solid renal tumor from a renal cyst. However, there is coincidence of renal carcinoma and simple renal cyst in about 2%–3% (literature range, 2%–7%) of cysts explored. Selective renal angiography is also very effective and can be performed if tomography is inconclusive. No technique is infallible, however, since a few tumors may become exceptionally cystic due to internal necrosis. Urine cytology has relatively little value at present in the diagnosis of renal cell adenocarcinoma. Metastatic carcinoma or malignant lymphoma in the kidney usually does not produce significant clinical or urinary findings.