ABSTRACT

We present a rare case of co-occurrence of Strongyloides stercoralis (S. stercoralis) infection and newly diagnosed pancreatic adenocarcinoma in a 71-year-old female who presented with new-onset jaundice and right upper quadrant abdominal pain. The patient had eosinophilia, recurrent Escherichia coli cholangitis, and a strong family history of jaundice in an endemic region. S. stercoralis larvae were identified on histopathological examination following pancreaticoduodenectomy. Notably, ivermectin treatment attenuated the delayed postoperative gastric emptying that had not responded to conventional management, including nasogastric decompression or drainage of a perigastric collection. While S. stercoralis can cause obstructive jaundice and pancreatic masses, this case highlights the importance of considering parasitic infections in patients from endemic areas or with immunosuppressive conditions who present with abdominal symptoms, particularly to avoid unnecessary interventions and prevent clinical deterioration.

INTRODUCTION

Strongyloides stercoralis is a parasitic nematode with the capacity for complex autoinfection, leading to dissemination of filariform larvae from the colon to the lungs, liver, central nervous system, or kidneys (1). Although globally prevalent, its incidence is likely underestimated due to limited data from endemic regions (2). Clinical manifestations vary widely and are typically classified as cutaneous, pulmonary, or intestinal. Cutaneous signs include larva currens and pruritus; pulmonary involvement may present as a Loeffler-like syndrome characterized by dyspnea, cough, and migratory pulmonary infiltrates; and gastrointestinal symptoms often include abdominal pain, diarrhea, and vomiting (3). Following the death of adult worms, a pronounced inflammatory response, termed the Mazzotti reaction, can occur and may require close patient monitoring (4, 5). If untreated, the parasitic infection can progress to life-threatening hyperinfection syndrome, particularly in immunocompromised patients (6). This case demonstrates a rare scenario in which S. stercoralis was detected intraoperatively in a patient undergoing surgery for presumed pancreatic malignancy.

CASE REPORT

A seventy-one-year-old female patient with hypothyroidism, primary hypertension, type II diabetes mellitus, and new-onset atrial fibrillation presented with jaundice, right upper quadrant abdominal pain, and loss of appetite. The patient’s past medical history was significant for two episodes of cholangiosepsis attributable to Escherichia coli, which required admission to the intensive care unit within the previous three months. The laboratory work-up at admission revealed neutrophilic leukocytosis (total white blood cell count: 16.2×10⁹/L), eosinophilia (1.2×10⁹/L), elevated acute-phase reactant (C-reactive protein: 115 mg/L), and direct hyperbilirubinemia (total bilirubin: 4.63 mg/dL). Abdominal computed tomography revealed a 32×25-mm hypodense lesion in the pancreatic head, invading the common bile duct and the main pancreatic duct, resulting in dilatation of the main pancreatic duct to 10 mm and of the intrahepatic bile ducts up to 9 mm. A retrospective review of preoperative imaging revealed no specific radiological signs suggestive of parasitic infection, such as bowel thickening or pneumatosis. The pancreatic head mass and biliary dilatation may have obscured subtle parasite-related changes (Figures 1 and 2). The patient underwent pancreaticoduodenectomy (Whipple procedure), which was extended to a total pancreatectomy and splenectomy due to positive surgical margins. Histopathological examination confirmed T2N2Mx pancreatic adenocarcinoma and revealed S. stercoralis in different forms, such as filariform larvae and adult worm from the gastric antrum to the distal duodenum (Figures 3 and 4). Detailed history of the patient revealed family members from the Black Sea region (7) with recurrent jaundice episodes, including a brother who died during jaundice workup without a cancer diagnosis. Postoperatively, the patient developed grade B delayed gastric emptying (DGE), unable to tolerate oral intake until postoperative day (POD) 19. Despite nasogastric decompression, symptoms of nausea and retching persisted. Diagnostic gastroscopy revealed an edematous narrowing of the efferent limb of gastrojejunostomy; however, the narrowing did not prevent advancing the scope distally, and a nasojejunal tube was inserted for enteral feeding. The resolution of the patient’s complaints paralleled the completion of medical treatment for S. stercoralis, allowing oral feeding at POD 19. Ivermectin 15 mg orally for two days was initiated to eradicate S. stercoralis. Following treatment, clearance of S. stercoralis was confirmed by stool and respiratory samples collected on day 10, with no larvae detected. The absence of larvae in stool and respiratory samples collected during and after ivermectin treatment confirmed the efficacy of the therapy. The patient subsequently received adjuvant chemotherapy for locally advanced pancreatic adenocarcinoma, with a regimen that included gemcitabine and capecitabine. The patient’s informed consent was obtained for publication.

DISCUSSION

This case presents an unusual coexistence of S. stercoralis infection and locally advanced pancreatic adenocarcinoma. While causality between these conditions cannot be established, the presence of parasitic forms throughout the gastrointestinal tract and improvement following ivermectin therapy suggest a significant parasitic contribution to postoperative complications.

Several clinical factors suggested parasitic infection rather than malignancy alone: A family history of jaundice in an endemic region, eosinophilia, acute onset of symptoms, and recurrent E. coli bacteremia. While S. stercoralis infection may cause malignancy-mimicking lesions in the pancreas (8), our patient had a histologically confirmed adenocarcinoma, indicating true coexistence of both conditions. The recurrent E. coli cholangiosepsis, which required hospitalization and intravenous antibiotic therapy, is particularly noteworthy as secondary bacterial superinfections may precede S. stercoralis infection. Hypothetical mechanisms include bacterial translocation through parasite-induced ulcers of the gastrointestinal mucosa, or bacteria carried on the larvae themselves (3). The absence of specific radiological features of strongyloidiasis highlights the challenge of preoperative diagnosis when malignancy coexists. The association between S. stercoralis infection and either obstructive jaundice or pancreatitis has been well established in multiple case series, particularly in patients with any degree of immunosuppression (9). Our patient’s diabetes and potential cancer-related immunosuppression may have predisposed them to parasitic proliferation. The relationship between atrial fibrillation and S. stercoralis remains speculative, though such an association has been reported in an elderly male patient with disseminated infection and long-term corticosteroid therapy (10).

The most notable aspect of this case was the resolution of DGE following ivermectin treatment. DGE is a common morbidity, occurring in up to 80% of pancreatic surgeries, including total pancreatectomy (11). The International Study Group of Pancreatic Surgery defines DGE as the inability to tolerate oral feeding and the requirement for prolonged nasogastric intubation after surgery (12). Pancreatic anastomotic leakage or perigastric collections after surgery are the most commonly encountered causes of DGE. NG decompression and drainage of perigastric collections, as needed, are the mainstays of DGE treatment. However, there was no significant drainage from the NG tube, and no perigastric collection was identified in this patient.

The temporal relationship between ivermectin treatment and DGE resolution strongly suggests that S. stercoralis contributed to persistent gastric dysmotility. S. stercoralis infection has been associated with gastrointestinal motility disorders (13), and the parasite can cause severe inflammation and edema in affected areas, leading to intestinal narrowing and obstruction (14). The persistent edema observed in the efferent limb of gastrojejunostomy during endoscopy may have resulted from ongoing parasitic inflammation. While postoperative fever, eosinophilia, and abdominal pain have been attributed to S. stercoralis infection (15, 16), DGE resolution following antiparasitic treatment has not been reported and represents a novel finding warranting further investigation.

The case underscores the diagnostic challenges of strongyloidiasis, which involves multiple testing modalities. Conventional stool analysis remains widely used but has notable disadvantages, being labor-intensive and requiring multiple stool samples to enhance parasitic yield (7) Advanced methods include the Baermann technique, which exploits larvae’s ability to transition to the free-living stage, and Harada-Mori filter-paper method, which utilizes larvae’s water tropism to concentrate them (17), though these remain time-consuming. Stool agar plates allow visualization of larval tracks on agar, but are costly, time-consuming, and pose potential safety risks to laboratory personnel (17). Serological testing has emerged as a promising non-invasive alternative; indirect immunofluorescence demonstrates a sensitivity of 97% and a specificity of 98% (18). However, the meta-analysis by Kalantari et al. (19) showed that the pooled sensitivity and specificity of serological assays were 71.7% [95% confidence interval (CI): 56.07% to 83.4%] and 89.9% (95% CI: 80.8% to 94.9%), respectively. A clear limitation of serology is its inability to differentiate past from active infections due to antibody persistence and cross-reactivity with other helminthic diseases (17). Additionally, molecular testing using polymerase chain reaction targeting 18S ribosomal DNA is another diagnostic modality with a specificity of 99-100%; however, sensitivity varies markedly with parasitic burden, decreasing to 15% in low-burden infections (20). A recently developed loop-mediated isothermal amplification assay with real-time polymerase chain reaction shows promising results but requires further validation (21, 22). Invasive diagnostic methods for S. stercoralis involve endoscopy with duodenal aspirate or biopsy, which can reveal eosinophilic infiltration, mucosal erosions, ulcerations, and granulomatous inflammation within the crypts, as observed in our case (17, 23). In cases of strong clinical suspicion, particularly in immunocompromised patients from endemic regions, empirical ivermectin treatment (one or more doses) may be warranted before confirmatory testing, given the high morbidity and mortality associated with untreated infection.

Ivermectin remains the drug of choice for S. stercoralis infection, with albendazole as an alternative therapy. A randomized trial involving 309 patients with non-disseminated Strongyloides infection showed equivalent efficacy of single- and multiple-dose regimens (85% vs. 86%; p=0.75), and single-dose therapy was better tolerated, although most adverse events were mild (24). We utilized a multiple-dose regimen with no adverse events and achieved successful parasite clearance.

S. stercoralis is an uncommon cause of gastrointestinal or hepatobiliary disease worldwide (25). A focused history, including travel to endemic regions, remains the most useful diagnostic tool (7). In patients from endemic areas presenting with obstructive jaundice, recurrent E. coli sepsis, and eosinophilia, the next step should be to order three consecutive stool samples (7). Performing seven consecutive stool examinations further increases the detection rate of rhabditiform larvae. When the burden of rhabditiform larvae is high, direct microscopic examination of the stool specimen reveals clear motility (6, 7). This case emphasizes the critical importance of considering parasitic infections in the differential diagnosis of obstructive jaundice, particularly in patients from endemic areas. However, the inability to definitively establish the causal relationship between S. stercoralis and DGE represents a significant limitation. Large-scale clinical studies are needed to investigate this potential association and establish evidence-based management protocols for patients with concurrent parasitic infections undergoing major abdominal surgery.