Renal and urinary tract masses: Pathology review

In the Emergency Department, two people came in. One of them is 68 years old Randy who has left flank pain and gross hematuria. On the physical examination, there’s also a palpable mass in the left abdomen. Randy also has a history of heavy smoking for the past 40 years. The other person is 54 year old Uriah who came in because of painless hematuria. A while ago, Uriah took cyclophosphamide for a condition he had called Hodgkin’s disease. Both individuals had an ultrasound done, which showed a mass in Randy’s left kidney and a mass in Uriah’s bladder.

Okay, Randy has a mass in his left kidney, while Uriah has a mass in his bladder. Let’s first talk about renal masses, which can develop in both adults and children. These masses may be either cysts or tumor. In turn, renal cysts can be either simple or complex, while tumors can be benign, like renal oncocytoma, or malignant, like renal cell carcinoma. Regarding masses of the urinary tract, the main concerns are transitional cell carcinoma and squamous carcinoma of the bladder.

Let’s look at them one by one. Simple cysts are very common and account for most of renal masses. They are typically small and occur in adults with otherwise healthy kidneys. On an abdominal ultrasound, they’re perfectly round and have a thin wall and are filled with fluid. This liquid is basically the produced by the kidney. The ultrafiltrate is the plasma without proteins that results after the filtration process, that happens in the glomeruli, specifically in Bowman’s capsule. This makes simple cysts anechoic on ultrasound, since the fluid does not produce an echo and thus appear black. Usually they’re asymptomatic and are discovered incidentally during an ultrasound or a CT-scan done for other reasons. On the other hand, complex cysts are larger than simple cysts. Additionally, on an ultrasound, they have thick, irregular walls and are multilocular- meaning they have septations within, that separate the cyst cavity into compartiments. Sometimes, complex cysts may even have a solid component within. Now, complex cysts are more likely to cause symptoms, like flank pain, for example. They also have a higher chance of becoming malignant and that’s why, for your tests, remember that complex cysts require additional follow up and even surgical removal.