Severe Chronic Tubulointerstitial Nephropathy in a Geriatric Pet Chinchilla (Chinchilla lanigera): A Case Report and Literature Review

Chronic renal disease is recognized in geriatric companion mammals, but detailed clinicopathological descriptions in chinchillas remain limited. An 11-year-old neutered female pet chinchilla (Chinchilla lanigera) with a six-month history of progressive weight loss and hyporexia developed acute clinical deterioration following approximately 8 h of indoor heat exposure (estimated maximum 29 °C). Anorexia, lethargy, absence of fecal output, and progressive dyspnoea preceded death. Necropsy revealed severe bilateral chronic renal lesions, gastrointestinal gaseous distension, and severe pulmonary congestion. Histopathology documented chronic tubulointerstitial nephropathy with interstitial fibrosis supported by Masson–Goldner trichrome staining and mineral deposits demonstrated by von Kossa staining. Periodic acid–Schiff staining highlighted glomerular and tubular basement membranes. Marked pulmonary vascular congestion was confirmed histologically, whereas pulmonary oedema and established pneumonia were not demonstrated in the examined sections. Together with the progressive terminal dyspnoea, these findings indicated clinically important respiratory abnormalities, although their underlying mechanism and contribution to death remained uncertain. Pure cultures of Klebsiella pneumoniae were recovered from six anatomical sites, with all isolates exhibiting an identical antimicrobial susceptibility profile and a reported multidrug-resistant phenotype. No bacterial-associated inflammatory lesions were identified in the histologically examined tissues, providing no morphological evidence of established disseminated septic disease. Given the uncertain time of death and a possible post-mortem interval of up to approximately 6 h, ante-mortem infection could not be reliably distinguished from perimortem dissemination or post-mortem translocation. Environmental heat exposure may have contributed to acute deterioration in an animal with severe chronic disease, although heat stroke could not be established retrospectively. This case supports a multifactorial interpretation and highlights the potential One Health relevance of antimicrobial resistance in companion animals, without demonstrating transmission.