Marbles, a 15-year-old tortoiseshell cat, presented at the clinic for a distended abdomen. She was eating and drinking normally with no other complaints. From a distance, she looked almost overweight. When palpating her abdomen, a large and firm mass was felt on her right side that seemed uncomfortable when touched. (Client consent was provided to include info and photos)
Upon completing a radiograph, a large, round structure was identified in her right abdomen with a soft tissue opacity. The right kidney could not be identified. An ultrasound was performed which identified the left kidney and a large, fluid filled mass in the right abdomen. Whenever you see a large mass in an older animal, cancer is something to keep on your list of differentials, a list of possible conditions or diseases that could be causing symptoms. A fine needle aspirate, a type of biopsy procedure, was performed on the mass and sent for analysis. The results came back as benign much to our relief. No cancer! Bloodwork was performed to check her organ function and if she had any signs of infection or anemia.
The decision was made with the client to perform surgery. A large incision was created from her xiphoid process, the smallest region of the breastbone, to her pubic bone. The large mass was identified to be a kidney affected by chronic pyelonephritis. 
Pyelonephritis is infection of the kidney. At this point, the right kidney was so severely affected, the kidney was no longer functional and filled with fluid. A nephrectomy (removal of the kidney) was performed. Almost 500 cc’s of fluid were drained from the kidney and the abdominal cavity to facilitate removal. This is not a surgery I have seen before and I appreciated the opportunity to scrub in to act as a surgeon’s assistant to the veterinarian.
Marbles recovered very well. She was up and eating not too long post-surgery. Since a kidney was removed, we noted to not provide nonsteroidal anti-inflammatory drugs (NSAIDs), for pain relief since they are contraindicated for kidney patients. She was provided other forms of pain relief and antibiotics to prevent infection. Marbles is a super sweet girl and was friendly and purring with all the staff. When I first met Marbles, pyelonephritis was not at the top of my list of differentials for the cause of her mass, especially since the mass was so large. Going forward, I will expand my list of different potential causes of abdominal masses to include pyelonephritis.
