Pyelonephritis in a Calf Secondary to Bacterial Cystitis

Abstract

Background: Cystitis and pyelonephritis are urinary tract conditions often associated with ascending bacterial infections that originate in the lower tract and progress to the kidneys. The anatomy of the female urinary tract, characterized by a short and straight urethra, predisposes animals to a higher incidence of infection, since this morphology facilitates the adherence, multiplication, and colonization of pathogenic bacteria in the bladder. Additional predisposing factors include omphalitis, urolithiasis, prolonged urinary catheterization, and systemic or local immunosuppression. Clinical signs typically include urinary frequency, dysuria, hematuria, hyporexia, abdominal pain, and discomfort, which may progress to systemic alterations in complicated cases. When untreated or in complicated cases, these signs may evolve to systemic alterations such as fever, dehydration, septicemia, and even death. Diagnosis is established by associating clinical manifestations with complementary exams such as urinalysis and urine culture. In fatal cases, necropsy and histopathological evaluation are indispensable to confirm the extension and severity of lesions. In neonates, an additional risk factor is failure of passive immunity transfer, since insufficient colostral intake markedly increases susceptibility to opportunistic or pathogenic bacteria, including those causing urinary tract disease. This report describes an unusual case of pyelonephritis secondary to cystitis in a 2-month-old male Braford calf, highlighting the probable contribution of inadequate colostrum ingestion, a previous history of omphalitis, and the serious clinical complications that can arise from this association.
Case: A 2-month-old male Braford calf was submitted for necropsy with a history of apathy, abdominal distension, polyuria followed by anuria, and dyspnea. Inadequate colostrum intake and a prior history of omphalitis were reported. Necropsy revealed enlarged kidneys with mild capsular adhesions. Multiple yellowish-to-reddish multifocal to coalescent areas, surrounded by dark red halos, extended from the renal cortex to the pelvis. The bladder exhibited uroperitoneum due to distension and contained a coppery-yellow liquid. The bladder wall showed thickening, fibrous cavitations, and an irregular mucosa with dark red and beige areas. These findings were consistent with necrosuppurative and hemorrhagic pyelonephritis associated with severe cystitis. Histopathological examination confirmed the presence of neutrophilic inflammatory infiltrates, extensive necrosis, and bacterial aggregates, supporting the diagnosis and demonstrating the severity of the infectious process.
Discussion: The progression from cystitis to pyelonephritis occurs via ascending infection and is most commonly described in female cattle. In this case, however, the disease occurred in a male calf, which is less common due to the urethral anatomy. The failure of passive immunity transfer resulting from insufficient colostrum intake, combined with a history of omphalitis, likely facilitated bacterial colonization of the urinary tract. The necrosis, suppuration, hemorrhage, and bacterial aggregates observed in the renal parenchyma are consistent with descriptions of pyelonephritis in cattle. The presence of uroperitoneum further reflects the severity of the condition. This case demonstrates that, even in young males, the association between ulcerative cystitis and necrosuppurative pyelonephritis may occur in the presence of predisposing factors. It also reinforces the importance of neonatal health management, particularly adequate colostrum intake, as a key preventive measure to reduce susceptibility to severe infectious diseases.

Keywords: cattle, young bovine, urinary tract, nephropathy, clinical diagnosis.

Descritores: bovinos, bezerro, trato urinário, nefropatia, diagnóstico clínico