AssessmentsRenal and urinary tract masses: Pathology review
USMLE® Step 1 style questions USMLE
A 52-year-old man comes to the clinic because of vague right-sided back pain over the past two months. He denies any recent trauma, heavy lifting, or new activity. The patient has also noticed a 4.2 kg weight loss during this time, despite not making any changes to diet or activity. The patient has a 20 pack-year smoking history. The patient’s temperature is 37.8°C (100°F), pulse is 75/min, and blood pressure is 128/85 mm Hg. Physical examination shows no abnormalities. The results of his urinalysis are shown below:
Content Reviewers:Yifan Xiao, MD
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.
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 compartments.
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.
Let’s now talk about renal oncocytoma, which is a benign tumor that usually appears in adults.
It originates from the intercalated cells of the collecting ducts.
Macroscopically, the tumor appears as a circumscribed mass with a central scar.
Microscopically, unlike RCC, a renal oncocytoma has large eosinophilic cells without perinuclear clearing.
Individuals can present with painless hematuria, flank pain and an abdominal mass.
Most of these benign tumors are resected in order to rule out malignancies, like RCC.
Moving onto renal cell carcinoma or RCC, which is the most common renal malignancy.
It usually appears in males between the ages of 50 to 70.
Risk factors for RCC include smoking and obesity.
It’s associated with mutations that cause gene deletions on chromosome 3.
These mutations can be sporadic or inherited as a part of Von-Hippel-Lindau syndrome, which is characterized by the formation of cysts and tumors in different parts of the body, like the kidneys and pancreas.
Now, RCC originates from the proximal convoluted tubule’s epithelial cells.
They appear clear on microscopy, because the standard tissue fixation and staining techniques dissolve the lipids and glycogen, leaving clear empty spaces behind.
Now, RCC can invade the renal vein and if it invades the renal vein on the left side, it can lead to a varicocele.
So, if RCC invades the left renal vein, then the venous drainage of the left testis is blocked, leading to a varicocele.
Remember for your exams that this can never happen on the right side, because the venous drainage from the right testis goes directly into the inferior vena cava.
Now that we got that covered, RCC can also invade the inferior vena cava via the renal veins and through hematogenous spread, can cause metastasis to the lungs and bones.
RCC can be asymptomatic, but it can also present with the classic triad of flank pain, hematuria and palpable masses.
That’s because if the tumor is big enough, it will compress the surrounding tissues, leading to flank pain and a palpable mass.
This compression can also damage the kidney, causing hematuria.
In more advanced stages, weight loss can also be present.
Now, RCC can also be associated with signs and symptoms of a paraneoplastic syndrome.
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