Hydrothorax secondary to a perinephric pseudocyst in a cat

The Omentum-A Forgotten Structure in Veterinary Surgery in Small Animals' Surgery

The greater and lesser omentum are derived from embryonic mesogastrium. The expansive greater omentum in dogs covers intestinal coils, while in cats, it is smaller. Comprising distinct portions, the greater omentum is rich in lymphatics and blood vessels. Conversely, the lesser omentum spans the liver, stomach, and duodenum. Studies on canine omentum reveal unique immune cell composition and regenerative potential attributed to adipose tissue-derived stromal cells (ADSCs). These cells hold promise in regenerative medicine, showing enhanced abilities compared with ADSCs from other sources. The omentum is critical in tissue repair and pathology, making it invaluable in veterinary surgery across various medical fields. The aim of this article was to research current knowledge about the applications of the omentum in veterinary surgery and the possibilities of using this structure in the future.

Case series: Pleural effusion caused by urinary ultrafiltrate in two cats without evidence of urinary obstruction, trauma, or simultaneous perinephric pseudocysts

Objectives

To describe the diagnostic techniques, surgical treatments, and outcomes of two cats with recurrent pleural transudate caused by urinary ultrafiltrate.

Animals

Two cats without evidence of trauma, urinary tract obstruction, or concurrent perinephric pseudocysts that were evaluated and treated for recurrent pleural transudate caused by urinary ultrafiltrate.

Study design

Short case series.

Methods

Multiphase contrast CT scan revealed leakage of contrast media from the kidneys bilaterally into the retroperitoneal spaces in both cats. Renal scintigraphy performed in one cat revealed progressive accumulation of 99mTc diethylenetriamine penta-acetic acid (Tc-DTPA) in the pleural space. Exploratory laparotomy localized the leakage of fluid to renal capsular defects bilaterally in both cats. The retroperitoneum was incised bilaterally to promote fluid drainage into the peritoneum, and nephropexies were performed.

Results

One cat had long-term survival with recurrent, though decreasing volumes of, pleural effusion. The second cat was euthanized 16 days postoperatively for progressive renal disease.

Conclusion

The diagnosis of spontaneous urinary ultrafiltrate accumulation in the pleural space of cats without evidence of trauma, urinary tract obstruction, or concurrent perinephric pseudocysts has not previously been reported. The surgical correction described reduced but did not completely eliminate the rate of pleural effusion accumulation.

Perioperative characteristics, histologic diagnosis, complications, and outcomes of dogs undergoing percutaneous drainage, sclerotherapy or surgical management of intrarenal cystic lesions: 18 dogs (2004-2021)

BACKGROUND

Canine intrarenal cystic lesions (ICLs) are infrequently reported in the veterinary literature. Several treatment options have been described including cyst fenestration (partial nephrectomy/deroofing) +/- omentalization, sclerotherapy using alcohol as a sclerosing agent, percutaneous cyst drainage (PCD), and ureteronephrectomy. Information regarding presenting clinical signs, physical examination findings, histologic diagnosis and outcomes of dogs with ICLs treated by different methods is limited. Medical records of 11 institutions were retrospectively reviewed to identify dogs that underwent PCD, sclerotherapy, surgical deroofing +/- omentalization, or ureteronephrectomy for management of ICLs from 2004 to 2021. Six weeks postoperative/post-procedural follow-up was required. Cases suspected to represent malignancy on preoperative imaging were excluded. The study objective was to provide information regarding perioperative characteristics, complications, and outcomes of dogs undergoing treatment of ICLs.

RESULTS

Eighteen dogs were included, with 24 ICLs treated. Ten had bilateral. There were 15 males and 3 females, with crossbreeds predominating. PCD, sclerotherapy, deroofing and ureteronephrectomy were performed in 5 (5 ICLs treated), 7 (11 ICLs), 6 (6), and 7 (7) dogs, respectively, with 5 dogs undergoing > 1 treatment. Seven dogs experienced 8 complications, with requirement for additional intervention commonest. PCD, sclerotherapy and deroofing resulted in ICL resolution in 0/5, 3/11 and 3/6 treated ICLs, respectively. Histopathology identified renal cysts (RCs) in 7/13 dogs with histopathology available and neoplasia in 6/13 (4 malignant, 2 benign). Of 5 dogs diagnosed histopathologically with neoplasia, cytology of cystic fluid failed to identify neoplastic cells. Among 7 dogs with histologically confirmed RCs, 4 had concurrent ICLs in ipsilateral/contralateral kidney, compared with 2/6 dogs with histologically confirmed neoplasia.

CONCLUSIONS

Benign and neoplastic ICLs were approximately equally common and cystic fluid cytology failed to differentiate the 2. Among renal-sparing treatments, deroofing most commonly resulted in ICL resolution. Presence of concurrent ICLs in ipsilateral/contralateral kidney does not appear reliable in differentiating benign from malignant ICLs.

Feline abdominal ultrasonography: what's normal? what's abnormal? The kidneys and perinephric space

PRACTICAL RELEVANCE

Abdominal ultrasound plays a vital role in the diagnostic work-up of many cats presenting to general and specialist practitioners. Ultrasound examination of the kidneys and perinephric space can provide important information on several conditions including chronic renal disease, hydronephrosis and perinephric pseudocyst formation.

CLINICAL CHALLENGES

Despite ultrasonography being a commonly used modality, many practitioners are not comfortable performing an ultrasound examination or interpreting the resulting images. Even for the experienced ultrasonographer, differentiating between incidental findings, such as a medullary rim sign, and pathological changes can be challenging.

AIM

This review, part of an occasional series on feline abdominal ultrasonography, discusses ultrasonographic examination of the normal and diseased kidney and perinephric space. Aimed at general practitioners who wish to improve their knowledge of and confidence in feline abdominal ultrasound, this review is accompanied by high-resolution images and videos available online as supplementary material. A subsequent article will address ultrasonography of the collecting system including the renal pelvis and urinary bladder.

EQUIPMENT

Ultrasound facilities are readily available to most practitioners, although use of ultrasonography as a diagnostic tool is highly dependent on operator experience.

EVIDENCE BASE

Information provided in this article is drawn from the published literature and the author's own clinical experience.

Resolution of nonurine transudative pleural effusion in a cat after removal of a hydronephrotic kidney

CASE DESCRIPTION A 3-year-old spayed female Bengal cat was evaluated because of a history of bilateral pleural effusion and hydronephrosis of the right kidney. CLINICAL FINDINGS Cytologic analysis of a pleural fluid sample revealed characteristics of a pure transudate with a high percentage of lymphocytes. Results of fluid biochemical testing were not consistent with urine or chyle. Serum biochemical analysis and echocardiography yielded no evidence of hypoalbuminemia or high hydrostatic pressure secondary to cardiac disease. Abdominal ultrasonography revealed hydronephrosis of the right kidney and hydroureter of the right ureter. TREATMENT AND OUTCOME Exploratory laparotomy with nephrectomy of the right kidney was performed. At the time of surgery, there was no evidence of communication between the retroperitoneal space and thoracic cavity. No other treatments were performed. No evidence of pleural fluid accumulation was detected 1 week after surgery, and no recurrence of clinical signs associated with pleural effusion was observed for > 1 year after surgery. CLINICAL RELEVANCE Transudative, or nonchylous lymphatic, pleural effusion secondary to intra-abdominal disease, but independent of a low plasma protein concentration, is uncommon in veterinary medicine. This case emphasized that urinary tract obstruction should be considered as a differential diagnosis for cats with pleural effusion when more common disorders are not identified. Even without evidence of direct communication between the abnormal kidney or retroperitoneal space and the pleural space, removal of the hydronephrotic kidney appeared curative.

Pleural effusion in the cat: a practical approach to determining aetiology

PRACTICAL RELEVANCE

Diverse disease processes result in sufficient fluid accumulation within the pleural space to cause respiratory compromise. Determining the underlying aetiology is key to appropriate management. This review outlines a practical approach to cases of pleural effusion, focusing on early recognition and confirmation of pleural space disease, stabilisation of the patient and logical diagnostic investigation. It emphasises the importance of a holistic approach, incorporating fluid analysis with other clinical data to determine the underlying aetiology.

CLINICAL CHALLENGES

Cats with pleural effusion often have severe respiratory compromise at presentation. Careful handling and prompt and adequate stabilisation, incorporating supplemental oxygen and therapeutic thoracocentesis, is essential to avoid respiratory failure. The typical, stepwise approach to the case must be adapted and the clinician may have to proceed, at least initially, without the luxury of information gained from a full history and physical examination. The challenge is to juggle stabilisation, localisation and confirmation of pleural effusion, owner communication and minimally invasive examination while remaining vigilant for clues that allow ranking of the differentials to formulate a diagnostic plan.

EVIDENCE BASE

Appropriately designed studies to determine the utility of diagnostic techniques in cases with confirmed aetiology are limited. The evidence supporting this review is grade II, III and IV, comprising a small number of prospective studies, several case series, reviews, extrapolation from other species, pathophysiological justification and combined clinical experience of those working in the field.

Unilateral improvement in glomerular filtration rate after permanent drainage of a perinephric pseudocyst in a cat

A 12-year-old, 6 kg, castrated male Siamese-cross cat was referred for investigation of an abdominal mass. The cat was found to have a left perinephric pseudocyst (PNP), accompanied by azotemia, with a small right kidney detected on ultrasound. Glomerular filtration rate (GFR) was determined by renal scintigraphy and was found to be low, with the left kidney contributing 64% of the total GFR. Percutaneous ultrasound-guided drainage of the PNP did not improve the GFR, and fluid reaccumulated within a short period of time. Laparoscopic fenestration of the cyst capsule was performed to allow for permanent drainage. The PNP did not recur, renal values progressively improved, and 8 months after the capsulotomy the GFR of the left kidney had increased by 50%, while renal function remained static on the right side.

Transitional cell carcinoma forming a perirenal cyst in a cat

An eight-year-old, neutered male Burmese cat presented with five days vomiting and anorexia. Physical examination, clinical pathology and diagnostic imaging findings suggested a perirenal pseudocyst. After partial resection of the perirenal capsule clinical signs temporarily resolved, but the cat was euthanased 34 days postoperatively as a result of seizures and recurrence of vomiting. Postoperative histopathology showed neoplastic transitional cells within and lining the resected perirenal capsule; a diagnosis of transitional cell carcinoma was confirmed post-mortem. To the authors' knowledge, this is the first report of this presentation of transitional cell carcinoma. Transitional cell carcinoma should be a differential diagnosis for the aetiology of perirenal pseudocyst.

Perirenal pseudocysts in 26 cats

OBJECTIVE

To evaluate clinical features, anatomical location, nature of pseudocyst fluid, results of surgical treatment and links with underlying renal disease in cats with perirenal pseudocysts.

DESIGN

A retrospective study of 26 affected cats, including 8 treated surgically.

RESULTS

Nineteen (73%) affected cats were male. The median age was 11 years. Most presented for abdominal enlargement and had varying degrees of renal dysfunction on presentation. Thirteen cats (50%) had bilateral pseudocysts. The pseudocyst fluid was a transudate or modified transudate in all cases. All surgically treated cats had subcapsular perirenal pseudocysts. Associated renal lesions were identified in all cats that had renal biopsies or detailed ultrasonographic examinations. Surgery relieved clinical signs but did not stop progression of renal disease. Cats survived a median of 9 months after surgery and survival was correlated statistically to degree of azotaemia at presentation. Percutaneous drainage of pseudocysts was ineffective in controlling long-term fluid accumulation.

CONCLUSIONS

Subcapsular perirenal pseudocysts are formed in cats by accumulation of transudate between the capsule and parenchyma of the kidney as a result of underlying parenchymal disease. Pseudocyst formation can occur at variable stages of renal dysfunction. Resection of the pseudocyst wall is usually effective in eliminating signs but does not stop progression of renal disease. The prognosis for cats with pseudocyst formation is related to the degree of renal dysfunction at time of diagnosis.

Omentalisation of perinephric pseudocysts in a cat

An 11-year-old male domestic shorthaired cat was presented with behavioural disturbances and abdominal distension of two days' duration. Haemobartonella felis was found on routine haematology and serum biochemistry showed mild azotaemia. Abdominocentesis revealed a transudate. Bilateral perinephric fluid accumulations were observed on ultrasonography and chronic nephrosclerosis was diagnosed on needle biopsies of the kidney. A celiotomy with resection of the major portion of both cyst walls was performed. The omentum was extended along the floor of the abdomen, across the ventral aspect of both kidneys and attached to the remnants of the pseudocyst wall. Ongoing physiological drainage was secured and cyst recurrence was prevented. Perirenal fluid was not detected at clinical and ultrasound follow-up examinations 14 days and seven months postoperatively. Mild azotaemia and refractory Haemobartonella infection were, however, still present.