Infected calyceal diverticulum in pregnancy: A rare case.

A calyceal diverticulum is a transitional epithelium-lined outpouching of a renal calyx which communicates with the main collecting system through a narrow infundibulum. There are two types of calyceal diverticula: type I, the most common, communicates with the minor calyx, and type II communicates with the major calyx or renal pelvis. Calyceal diverticula are rare and mostly found incidentally; however, they can cause urinary tract infection symptoms (e.g., hematuria, pain, and fever). Diagnosing an infected calyceal diverticulum during pregnancy is particularly challenging due to overlapping symptoms and the limitations of imaging modalities that avoid ionizing radiation. Prompt diagnosis and treatment are necessary to avoid irreversible renal dysfunction and/or urological surgery. Currently, there are no established treatment guidelines for diagnosing and managing infected calyceal diverticula in pregnant patients. The rarity of this condition and the complexities introduced by pregnancy create challenges in standardizing care and determining the optimal treatment strategy, timing of interventions, and the impact on maternal and fetal outcomes. A 29-year-old primigravid woman presented emergently to the hospital at 15 weeks and 4 days gestation with concerns of severe right-sided flank pain and hematuria. Initial renal ultrasound revealed a complex, hypovascular lesion in the interpolar region of the right kidney measuring 6.9 × 6.8 × 3.7 cm, suspicious for mass versus pyelonephritis with associated phlegmon. Further characterization of the lesion by MRI revealed communication between the lesion and the mid-pole collecting system. Differential diagnoses included infected calyceal diverticulum, hydronephrosis of a duplicated system, renal abscess, and infected urinoma. Through a multidisciplinary approach, including ultrasound-guided placement of a drainage catheter at 16 weeks gestation, and tailored intravenous antibiotic therapy, the patient delivered a 3379 g male at 40 weeks and 0 days gestation. This case highlights the potential for conservative management in the absence of clear guidelines and underscores the importance of collaboration among obstetrics, urology, infectious disease, and interventional radiology teams. The implications of this case extend to increasing awareness of calyceal diverticula as a differential diagnosis in pregnant patients presenting with atypical urinary symptoms. It emphasizes the necessity of a multidisciplinary approach to ensure both maternal and fetal safety and offers valuable insights that could inform future cases, contributing to the development of more concrete guidelines for managing infected calyceal diverticula during pregnancy. Consent was obtained from the patient and IRB approval was not required for this case.