Secondary pelvic hydatid cyst of the Douglas pouch causing ureteral obstruction and acute pyelonephritis: A rare case report

Abstract

Introduction

Hydatid disease caused by Echinococcus granulosus primarily affects the liver and lungs. Pelvic localization is rare, and cysts in the Douglas pouch are exceptional. Urinary tract involvement through extrinsic compression leading to hydronephrosis and pyelonephritis is exceedingly uncommon.

Case presentation

We report a 47-year-old Tunisian male with mental retardation who presented with fever, flank pain, and dysuria. Laboratory workup revealed leukocytosis and positive urine culture for Escherichia coli. Contrast-enhanced CT showed multiple hepatic and peritoneal hydatid cysts, the largest measuring 13 × 11 cm in the liver, and a 12 × 10 cm cyst in the Douglas pouch compressing the right ectopic ureter. This caused marked uretero-pyelo-calyceal dilatation and secondary acute pyelonephritis of the right kidney. The patient was treated with intravenous antibiotics and urinary decompression by double-J stenting, followed by albendazole and elective surgery including excision of the pelvic cyst and partial pericystectomy of hepatic lesions. Postoperative recovery was uneventful, and at 6-month follow-up the patient remained asymptomatic without recurrence

Discussion

Hydatid cysts of the Douglas pouch are extremely rare and may mimic other pelvic pathologies. Involvement of the urinary tract by extrinsic compression is exceptional and can present as recurrent urinary infections or acute pyelonephritis. Imaging plays a crucial role in diagnosis, while surgery remains the mainstay of treatment, supported by antiparasitic therapy.

Conclusion

Hydatid cysts in the Douglas pouch should be considered in the differential diagnosis of pelvic cystic lesions in endemic regions, particularly when associated with urinary tract obstruction.

Highlights

• •Hydatid cysts of the Douglas pouch are extremely rare but clinically significant.
• •Pelvic hydatid cysts may compress adjacent structures such as the ureter, causing urinary obstruction.
• •Early diagnosis and timely surgical management prevent complications like pyelonephritis and renal damage.
• •Awareness of hydatid disease and public health measures are crucial in endemic regions.

Introduction

Hydatid disease is a zoonotic infection caused by the larval form of Echinococcus granulosus. It is endemic in North Africa, the Middle East, South America, and parts of Asia. The liver (up to 70 %) and lungs (20–30 %) are the most frequently involved organs due to first-pass clearance in the portal and pulmonary circulations [1].

Peritoneal hydatidosis accounts for about 5–10 % of cases, usually secondary to rupture or surgical spillage of hepatic cysts. Primary pelvic hydatidosis is exceptional, particularly in the Douglas pouch, and can mimic gynecological, urological, or gastrointestinal masses [2]. Involvement of the urinary tract through extrinsic compression is extremely uncommon.

We report a rare case of a 47-year-old mentally retarded patient presenting with acute pyelonephritis due to extrinsic ureteral obstruction by a Douglas pouch hydatid cyst, in the context of disseminated hepatic and peritoneal hydatidosis. The case is presented in line with the SCARE criteria [3].

Case presentation

A 47-year-old man from a rural endemic region in Tunisia, with a history of mental retardation and no prior surgical or hydatid disease, presented to the emergency department with a five-day history of fever, right flank pain, and dysuria. On physical examination, he was febrile (39.2 °C) and exhibited right flank tenderness without signs of peritoneal irritation. Laboratory investigations revealed leukocytosis (16,500/mm³; normal range 4000–10,000/mm³) with neutrophilia and an elevated C-reactive protein level (120 mg/L; normal <5 mg/L). Renal and liver function tests were within normal limits (creatinine 80 µmol/L; normal 60–110 µmol/L). Urinalysis showed pyuria and bacteriuria, and urine culture grew Escherichia coli sensitive to cephalosporins.

The diagnostic approach followed standard steps: abdominopelvic ultrasonography revealed multiple cystic hepatic lesions with internal septations consistent with hydatid cysts. A chest radiograph showed no pulmonary involvement. Contrast-enhanced abdominal CT demonstrated hepatomegaly with multiple well-defined, multivesicular cystic lesions involving all liver segments, the largest measuring 13 × 11 cm in segments II and III. Additional multiple peritoneal and retroperitoneal hydatid cysts were identified. Notably, a large cyst measuring 12 × 10 cm was located in the Douglas pouch, compressing the right ectopic ureter and causing marked uretero-pyelo-calyceal dilatation (40 mm) upstream. The right kidney displayed diffuse cortical hypodense areas consistent with acute pyelonephritis (Fig. 1), while the left kidney was of normal size, morphology, and function.

Fig. 1.

Contrast-enhanced CT scan (coronal view) showing a large hydatid cyst in the Douglas pouch measuring approximately 12 × 10 cm (Blue arrow). The cyst compresses the right ectopic ureter, resulting in marked uretero-pyelo-calyceal dilatation (Red arrow). Multiple hepatic and peritoneal hydatid cysts are also visible.

The patient was initially managed with intravenous ceftriaxone (2 g/day) and gentamicin (3 mg/kg/day), resulting in clinical improvement and defervescence within 72 h. A right double-J ureteral stent was subsequently placed to relieve the obstruction. The infection stabilized, and Albendazole therapy (10 mg/kg/day) was initiated for two weeks before surgery to reduce cyst viability and minimize the risk of intraoperative spillage.

Surgical intervention was performed via midline laparotomy. Intraoperatively, a well-encapsulated hydatid cyst of the Douglas pouch was identified. A resection of the protruding dome of the cyst was performed, combined with partial pericystectomy of accessible superficial hepatic cysts. Hypertonic saline was used intraoperatively to minimize the risk of spillage. Histopathological examination confirmed hydatid disease by demonstrating laminated and germinal membranes (Fig. 2).

Fig. 2.

Intraoperative photograph demonstrating the Douglas pouch hydatid cyst before (A) and after (B) resection of the protruding dome. The cyst was carefully dissected and partially resected.

Postoperative recovery was uneventful. The patient was discharged on postoperative day seven with continuation of oral albendazole therapy for three months. At six-month follow-up, he remained asymptomatic, with normal renal function and no radiological evidence of recurrence.

Discussion

Hydatid disease remains an endemic zoonosis in Tunisia and North Africa, sustained by close contact between dogs and livestock. The national incidence in Tunisia ranges from 12 to 15 cases per 100,000 inhabitants annually [4], reflecting persistent transmission despite control efforts.

In Tunisia, the life cycle of Echinococcus granulosus involves dogs as definitive hosts and sheep or other herbivores as intermediate hosts. Humans become accidental intermediate hosts through ingestion of parasite eggs from contaminated food, water, or direct contact with infected dogs [4]. Once ingested, the oncospheres penetrate the intestinal mucosa and reach the portal circulation, primarily lodging in the liver and lungs. Secondary peritoneal or pelvic involvement typically results from cyst rupture, surgical spillage, or hematogenous spread. Rarely, isolated pelvic cysts may arise from lymphatic dissemination or implantation of scolices in the pelvic peritoneum [4].

While the liver and lungs are the most frequently affected organs, accounting for up to 70 % and 20–30 % of cases respectively, peritoneal involvement is uncommon, representing approximately 5–10 % of all cases [1], [2].

Pelvic hydatid cysts, particularly those located in the Douglas pouch, account for 5–10 % of cases, with few cases reported in the literature. These cysts are often secondary to intraperitoneal dissemination from hepatic or splenic lesions, although primary peritoneal involvement has also been described [5].

Clinical manifestations of pelvic hydatid cysts depend largely on the size and location of the lesion. In most cases, symptoms are vague or absent until the cyst exerts pressure on adjacent organs. Compression of the urinary tract is an exceptional complication [6], which can lead to hydronephrosis, recurrent urinary tract infections, or, as in our patient, acute pyelonephritis. This unusual presentation underscores the importance of considering hydatid disease in the differential diagnosis of pelvic masses, particularly in endemic areas, even when urinary symptoms predominate.

Imaging plays a crucial role in the diagnosis and preoperative planning of hydatid disease [7]. CT scan typically reveals well-defined cystic lesions, often with internal daughter cysts, while MRI can provide further characterization of cyst content and its relationship with surrounding structures. In extra-hepatic disease, serological tests may be negative or inconclusive, limiting their diagnostic value, and highlighting the reliance on radiological findings.

Management of pelvic hydatid cysts requires a multidisciplinary approach. Infection control is paramount in cases complicated by pyelonephritis, often necessitating intravenous antibiotics and urinary drainage prior to definitive surgical intervention. Surgical excision remains the treatment of choice, with total cystectomy preferred when feasible to minimize the risk of spillage and recurrence [8]. Intraoperative precautions, such as the use of scolicidal agents and careful dissection, are essential. Adjuvant albendazole therapy is recommended in cases of incomplete resection, rupture, or multiple cysts, as it reduces the risk of recurrence and secondary dissemination [9].

In our patient, the combination of infection control, ureteral decompression, albendazole therapy, and elective surgical excision resulted in favorable outcomes, with resolution of pyelonephritis and no recurrence at six-month follow-up. This case highlights the importance of early recognition, careful imaging assessment, and staged management in patients with complex presentations of disseminated hydatid disease.

Conclusion

Douglas pouch hydatid cysts are exceptionally rare. Their presentation with ureteral obstruction and acute pyelonephritis is even more unusual. Hydatid disease should be considered in the differential diagnosis of pelvic masses in endemic regions. Beyond clinical management, prevention through community education, veterinary surveillance, and intersectoral collaboration within the One Health framework is crucial to reducing disease incidence in endemic countries.

Ethical approval

This is a case report. Therefore, it didn't require ethical approval from the ethics committee of Mohamed Taher Maamouri university hospital – Nabeul, Tunisia.

Funding

The study did not receive any grant from funding agencies in the public, commercial or not-for profit sectors.

Patient Consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

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CRediT authorship contribution statement

Amine Abdelhedi: Validation, Supervision, Software. Houda Gazzah: Investigation, Formal analysis, Data curation. Hassen Touinsi: Writing – review & editing. Mahdi Bouassida: Writing – review & editing, Visualization, Validation. Ghazi Lâamiri: Writing – original draft, Resources, Methodology, Investigation. Hazem Alouani: Writing – original draft, Resources, Methodology, Investigation, Formal analysis, Data curation, Conceptualization.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.