A Rare Case of Retroperitoneal Abscess Caused by Nephro-Colic Fistula Resulting from Staghorn Calculus

Background

Nephro-colic fistulas (NCF) are infrequent and generally linked to inflammatory, infection, trauma, or neoplastic phenomena. The symptomatology is often aspecific and not very evocative at first. The diagnosis is usually based on radiological or endoscopic examinations.

We report the case of a patient who presented with a retro-gastric and left retro-renal abscess related to the protrusion of a staghorn lithiasis within the colonic lumen. The abscess could have been a result of several inflammatory episodes of the colon. The only possibility to treat it was surgery, but the absence of guidelines about this phenomenon makes the management of this medical condition difficult. Some similar cases are described in the literature. We add a new atypical clinical case associated with an iconography rarely seen for this pathology. The purpose is to explain our approach and discuss the literature of NCF associated with coralliform calculus.

Case Report

A 68-year-old women with a history of anticoagulated atrial fibrillation, left renal atrophy, diverticulitis, large incisional hernia, and a body mass index of 45 presented to the Emergency Department in November 2022 with dyspnea and chronic abdominal pain having evolved over several months, but without transit troubles or fever.

During the clinical examination, the patient had polypnea and presented a diffuse pain in the upper abdomen. There were unrelated edemas of the lower limbs and a large incisional hernia already present. The cardio-pulmonary auscultation was normal, apart from a high respiratory rate. The biological results showed a significant increase in the inflammatory syndrome, D-dimer levels, and N-terminal pro-B-type natriuretic peptide, as well as indirect signs of sepsis, including hyperbilirubinemia and hyperlactatemia.

The thoraco-abdominal computed tomography (CT) scan ruled out a pulmonary embolism and revealed a left pleural effusion and a retro-gastric and left retro-renal abscess. She also presented with a 25×30 mm staghorn lithiasis of the atrophied left kidney. No previous CT scan was found.

The patient was hospitalized and received antibiotic therapy with amoxicillin-clavulanic acid during 72 h. Initially, a retro-gastric perforation was highly suspected. However, it was excluded due to the absence of contrast agent extravasation after ingestion.

Three days after admission, a new CT scan showed an unfavorable evolution of the retro-gastric abscess measuring 9×6 cm and a peri-splenic component measuring 4×3×17 cm extending in the left parieto-colic gutter to the left iliac fossa (Figure 1).

Immediately, the patient underwent percutaneous drainage of the retroperitoneal abscess by a radiologist. A large post-puncture hematoma ensued, requiring a second drainage the following day. Moreover, a new sepsis occurring after the drainage led the patient to be moved to the Intensive Care Unit. The origin of this sepsis was multifactorial, including an associated pulmonary infection. The abdominal germs found were Escherichia coli and were resistant to amoxicillin-clavulanic acid. The antibiotic therapy was adapted to piperacilline/tazobactam, according to the bacteriological results.

The fifth day, after stabilization, another CT scan illustrated a slight regression of the drained retroperitoneal abscess. Its origin being unclear, various radiological opinions were requested. Following the visualization of a left intra-renal gas bubble and a staghorn calculus, a left colo-renal fistula was highly suspected.

A colonic enema did not allow the observation of an NCF (Figure 2). However, a colonoscopy confirmed the presence of a coralliform lithiasis protruding within the colonic lumen (Figure 3). A left colonic diverticulosis was also demonstrated. The gastroscopy showed a non-perforated bulbar ulcer, treated by proton pump inhibitor.

After 2 weeks of piperacilline/tazobactam and 17 days of hospitalization, the patient underwent a left segmental colectomy (Figure 4), left total nephrectomy, splenectomy, and flattening of the retroperitoneal abscess by laparotomy. The incisional hernia was treated by abdominal wall closure using a polydioxanone suture after placement of a Vicryl mesh over the intestines.

The immediate postoperative course was uneventful. The patient gradually regained transit. At the end of hospitalization, the radiological control did not show any recurrence of the abscess. She stayed in our Surgery Department for 1 month and subsequently benefited from revalidation, due to mobilization difficulties.

A few weeks later, she was hospitalized for cardiac decompensation, disrupting the follow-up. She also had a pulmonary embolism and stayed 2 more months at the hospital. The thoraco-abdominal CT performed during these events showed a positive abdominal evolution without recurrence of the abscess and incisional hernia.

Discussion

NCF are not common but are nevertheless well described in the literature. Their origin is diverse. Renal or colic inflammatory phenomena, trauma, stones, tuberculosis, and neoplasia are the main sources. Symptoms are often nonspecific, such as abdominal pain, nausea, and vomiting, and the only suggestive signs are pneumaturia or fecaluria.

The presence of an NCF associated with the passage of a lithiasis is a pathology rarely encountered. The first description of this phenomenon was published by Narins et al [1] in 1959 in a case report. During surgery, a para-rectal abscess linked to a rectal perforation was found at the height of the lithiasis, which had become obstructive but without absolute proof that the calculus was responsible. A few case reports with similarities are described in the literature [2–8]. A common finding is the presence of a staghorn lithiasis located at the level of the fistula. Stones are usually composed of struvite-carbonate-apatite [3]. They increase morbidity and mortality when they are not treated [2,3]. No incidence is reported in the literature about NFC associated with a calculus.

For detection, the abdominal CT scan is the criterion standard [7]. Nevertheless, the radiological diagnosis remains complicated. Colonic enema and colonoscopy can help with diagnosis if a doubt subsists. In our case, the colonoscopy allowed us to confirm the radiological suspicion.

Colonic inflammatory phenomena linked to multiple recurrences of diverticulitis in our patient could have been the cause of the problem [6,9]. The pathology of the surgical specimen showed numerous diverticula present in the resected area. We suggest that covered perforated diverticulitis was the origin of the fistula and abscess.

Some studies report the calculus as the only etiology of a fistula [3,5]. Myers et al [10] already described in 1974 an increased risk of renal fistula in the event of radiological atrophy of the perirenal fat. Our patient was known to have a left kidney, described radiologically as atrophic, associated with a voluminous lithiasis. These elements could have had a role in the formation of the fistula.

The treatment of an NCF associated with lithiasis is surgery, including nephrectomy and colectomy, with immediate colonic anastomosis if possible [7,8]. Nevertheless, there is no consensus about the surgical management. Percutaneous nephrolithotomy is another therapeutic option only when there is no fistula; however, some studies describe an increase in NCF since the use of this technique [11].

This atypical case was highly discussed with urologists and radiologists. We chose to improve the clinical condition of the patient with antibiotherapy and radiological drainage of the abscess before surgery, owing to comorbidities, anticoagulated treatment, and unclear origin of the abscess. The surgery was thus able to be performed in the best conditions. We observed a fast positive recovery.

The treatments described in the literature are commonly antibiotics and surgery [2,3,6,8]. Due to the atypical chronology of these cases, the management varies hugely.

Conclusions

This clinical case once again shows the diagnosis difficulty of NCF and the complexity of the management. The symptomatology of this pathology is generally nonspecific, and the treatment is always surgical. Today, there are no treatment plans or guidelines for this rare case report.