Concurrent occurrence of congenital peritoneopericardial diaphragmatic hernia and portosystemic shunt in a Persian cat: diagnostic challenges and clinical implications

Technical Summary: Concurrent Congenital Peritoneopericardial Diaphragmatic Hernia and Portosystemic Shunt in a Persian Cat

Problem Statement
Peritoneopericardial diaphragmatic hernia (PPDH) and congenital portosystemic shunts (PSS) are distinct, uncommon developmental anomalies in felines. While PPDH involves the abnormal communication between the pericardial sac and abdominal cavity, PSS involves vascular communications allowing portal blood to bypass the liver. Although both conditions are individually well-documented, their concurrent occurrence has rarely been reported. This co-occurrence presents a significant diagnostic challenge, as the clinical and clinicopathologic signs of PSS (neurologic and gastrointestinal disturbances) can mask or be confused with the variable presentation of PPDH, potentially leading to incomplete diagnosis and management.

Methodology
The study presents a case report of a 3-year-old neutered male Persian cat presenting with persistent vomiting, diarrhea, anorexia, lethargy, ataxia, and intermittent head pressing. The diagnostic and therapeutic approach followed a staged protocol:

1. Initial Clinical and Laboratory Assessment: Physical examination revealed depression, dehydration, and pale mucous membranes. Hematology showed mild microcytic non-regenerative anemia. Serum biochemistry indicated markedly decreased blood urea nitrogen (BUN) and urea, mild elevations in hepatic enzymes (AST, ALT), and severe fasting hyperammonemia, raising suspicion for PSS.
2. Imaging and Initial Diagnosis: Abdominal ultrasonography unexpectedly identified herniation of hepatic tissue and the gallbladder into the pericardial sac. This was confirmed via thoracic radiography and echocardiography as PPDH.
3. Staged Surgical Management:
   • Phase 1 (PPDH Repair): Following medical stabilization (fluids, antibiotics, antiemetics, and vitamin supplementation), surgical correction of the diaphragmatic defect was performed using a PGA 2/0 suture to close the hernial ring.
   • Phase 2 (Post-Operative Stabilization): The patient underwent a one-month recovery period with medical management to control potential hepatic encephalopathy associated with the suspected PSS.
   • Phase 3 (PSS Diagnosis and Repair): After recovery, computed tomography angiography (CTA) was performed, identifying a congenital extrahepatic shunt between the left gastric vein and the left phrenic vein. Surgical attenuation was subsequently performed via medial celiotomy using cellophane banding to induce gradual fibrosis and reduction of shunt flow, secured with surgical clips.
4. Follow-up: The cat was monitored for clinical signs and clinicopathologic parameters at 6 months post-second surgery.

Key Results

• Diagnostic Findings: The case confirmed the presence of two distinct congenital anomalies: a PPDH with hepatic and gallbladder displacement, and a left gastro-phrenic extrahepatic portosystemic shunt.
• Clinical Outcome: Following the staged surgical interventions, the cat's clinical signs (neurologic and gastrointestinal) progressively resolved.
• Laboratory Outcomes: Clinicopathologic abnormalities, including microcytic anemia, decreased BUN, and elevated hepatic enzymes, returned to reference intervals by the 6-month follow-up.
• Long-term Status: At the 6-month re-evaluation, the cat remained clinically normal with no recurrence of neurologic or gastrointestinal signs, and all hematologic and biochemical values were normalized.

Significance and Claims
The authors assert that this report documents a rare concurrent occurrence of PPDH and congenital PSS in a cat, a combination not previously well-defined in the literature. The primary significance of the work lies in its demonstration of the diagnostic challenges inherent when multiple congenital defects coexist. Specifically, the paper emphasizes that:

1. Diagnostic Vigilance: The identification of one congenital anomaly (PPDH) should not preclude the investigation of additional developmental defects, particularly when clinical and laboratory findings (such as severe hyperammonemia and neurologic signs) are not fully explained by the initial diagnosis.
2. Value of Staged Approach: A staged diagnostic and therapeutic strategy—prioritizing the repair of the PPDH to ensure anesthetic safety and physiologic stability, followed by the definitive diagnosis and attenuation of the PSS—is effective for managing complex coexisting congenital disorders.
3. Imaging Utility: Advanced imaging, specifically CTA, is highlighted as the gold standard for the definitive characterization of vascular anomalies and surgical planning in such cases.
4. Therapeutic Success: The successful use of cellophane banding for gradual attenuation, following a period of medical stabilization, resulted in favorable long-term outcomes, reinforcing the efficacy of this technique for extrahepatic PSS in cats.

The paper concludes that comprehensive evaluation is critical in patients with congenital anomalies to ensure successful management of coexisting conditions.