Introduction

Subacute intestinal obstruction is a frequently encountered surgical emergency. It is commonly caused by strictures, polyps, and tumors, while gallstones or foreign bodies are rare contributors. Although uncommon, enteroliths can also lead to intestinal obstruction, typically forming proximal to a stricture, within a diverticulum, or in a blind loop (1). Enterolithiasis is broadly categorized into primary and secondary categories.  The primary enteroliths develop within the small intestine, typically inside an abnormal pouch like a diverticulum. In contrast, secondary enteroliths originate in the gallbladder (2,3) or as renal stones, which can migrate into the gastrointestinal lumen through a fistulous tract (4). 
Diverticular ailment of the small intestine is a major cause, trailed by intestinal strictures resulting from infectious conditions like tuberculosis or inflammatory disorders such as Crohn’s disease (5). India bears the highest tuberculosis burden, contributing to 26% of global cases (7). Extrapulmonary tuberculosis (EPTB) makes up 16% of the 7.5 million informed TB cases worldwide and 19% in the Southeast Asian province. But in India, abdominal tuberculosis counts for 11-13% of all EPTB cases (7).
Intestinal tuberculosis leads to stricture formation, obstructing intestinal flow and creating an environment conducive to stone formation. However, enteroliths remain a rare occurrence in tuberculosis, as most patients either remain asymptomatic or their symptoms are not directly linked to enteroliths (5). The finding is primarily grounded on a detailed medical history, physical investigation, and radiologic imaging (4).
We present a case of enterolithiasis secondary to ileal stricture likely due to abdominal tuberculosis who was hepatitis B positive and presented as subacute intestinal obstruction.

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Case presentation

A 48-year-old female patient came to our facility, IMS & SUM Hospital, Bhubaneswar, India, with a 10-day history of abdominal pain and non-passage of stool and bilious vomiting for 2 days. The pain was colicky in nature and moderate in intensity. She also reported a weight loss of approximately 5kg in a 1-month duration. No history of fever, cough, or diarrhea. She was passing flatus intermittently. Her medical history reveals prior treatment for pulmonary tuberculosis 16 years ago, consisting of a 2-month treatment of ethambutol, isoniazid, pyrazinamide, and rifampicin, tracked by 4 months of rifampicin and isoniazid. Additionally, she received a transfusion of three packed red blood cells 1 year ago for anemia. The patient had no report of earlier abdominal surgery. 
On investigation, the abdomen was found soft and mildly distended, without any scars. The umbilicus was inverted, mild diffuse tenderness was present, and bowel sounds were sluggish. Rectal examination was unremarkable. A general examination revealed normal findings apart from the presence of pallor.
The investigations showed hemoglobin 10.5g/dL; whole and differential counts were normal; The liver function test was deranged, showing total bilirubin of 1.69 mg/dL, direct bilirubin of 1 mg/dL, aspartate aminotransferase  of 255 IU/L, alanine aminotransferase  of 173 IU/L, and alkaline phosphatase of 96 IU/L. The patient's hepatitis B surface Antigen titer was 4660 IU/mL, suggesting the presence of a hepatitis B infection. The chest radiograph showed radio-dense opacifications in the B/L lung fields (Figure 1). An erect radiograph of the abdomen showed dilated small bowel loops and a single radio-opaque shadow in the pelvis, which has a central less dense area with a peripheral dense rim, giving it a laminated appearance (Figure 2a). Computed tomography of the abdomen with contrast (CECT) revealed a largely walled radio-dense concentric calculus with few air foci within the ileal loop and resultant proximal bowel loop dilatation (enterolith in the ileum causing subacute intestinal obstruction) (Figure 2b).

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Figure 1

Chest radiograph showing multi-focal patchy nodular air space opacities seen in bilateral upper, midzones and right lower zone. A few tiny nodular opacities are also seen in the right lower zone. Yellow arrows indicate the opacities.

Figure 2(a)

Erect radiograph of the abdomen displaying dilated small bowel loops with an oval radio-dense opacity in the pelvis. The blue arrow indicates the radio-dense opacity, while the yellow arrows point to the dilated small bowel loops.

 

Figure 2(b)

CECT of the abdomen with a blue arrow representing enterolith in the ileum. CECT  computed, tomography of the abdomen with contrast.
 

Exploratory laparotomy was planned on day 3 of the admission. Intraoperatively, a single stricture was identified 50 cm proximal to the ileocecal junction (Figure 3a). Just proximal to the stricture, a firm, hard, oval structure was palpated, raising suspicion of a stone. Mesenteric lymph nodes were also enlarged. Two lymph nodes were excised, each for Cartridge-Based Nucleic Acid Amplification Test (CBNAAT) and biopsy. A longitudinal incision was made along the antimesenteric border at the stricture site, extended 1-2 cm proximally and distally onto normal bowel tissue (Figure 3b). This allowed access to the stone, measuring 5 cm × 4 cm, black in color, and hard in consistency, which was successfully extracted (Figure 3c). Two stay sutures were placed at the ends of the stricture opening and pulled perpendicularly to the bowel’s long axis to stabilize it. The enterotomy was closed transversely with 2-0 vicryl sutures to ensure a secure closure. The abdomen was inspected for bleeding or contamination, irrigated, and the wound was closed in layers with a sterile dressing applied. The post-operative phase was monotonous, and the patient was discharged after 3 days. Biochemical analysis showed that stone was rich in calcium carbonate and calcium phosphate. Histopathological examination of the mesenteric lymph node showed a granuloma suggestive of TB (Figure 3d). But CBNAAT was negative. The patient was on antitubercular treatment, consisting of a 2-month treatment of ethambutol, isoniazid, pyrazinamide, and rifampicin, followed by 4 months of rifampicin and isoniazid, and ethambutol. The patient was followed up after 4 and 8 weeks for clinical assessment and liver function tests to monitor for drug-induced hepatotoxicity. There were no complaints of abdominal pain or fever, no abdominal distension, and no weight gain was observed.
In our case, only one plain radiograph was done, and as the patient was stable and presented with subacute obstruction, CT of the abdomen was possible, which gave a confirmatory diagnosis of enterolith.

 

Figure 3(a)

The arrow indicates an ileal stricture located 50 cm proximal to the ileocecal junction, with a proximal dilated segment and distal collapsed segment.

 

Figure 3(b)

Enterotomy with stone being visible.

 

Figure 3(c)

Enterolith; black in colour, measuring 5 cm x 4 cm.

 

Figure 3(d)

A biopsy slide showing granulomas suggestive of TB on H&E stain (40× magnification); arrow showing caseous necrosis. TB, Tuberculosis.​

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Discussion

Small bowel obstruction, a communal surgical emergency, is classified into three types: extraluminal obstruction (caused by factors such as adhesions, hernias, carcinomas, or abscesses outside the bowel), intrinsic obstruction (due to issues within the bowel wall, often primary tumors), and intraluminal obstruction (caused by blockages inside the bowel, such as gallstones, enteroliths, foreign bodies, or bezoars) (8).
Enterolithiasis is a comparatively infrequent condition that occurs in parts of intestinal stasis, often associated with conditions such as intestinal diverticula, side-by-side afferent loops in Billroth II gastrojejunostomy or Roux-en-Y procedures, blind pouches, enteroanastomoses, incarcerated hernias, small intestinal tumors, kinking from intra-abdominal adhesions, stricturing seen in Crohn’s disease, and intestinal tuberculosis (9). The colon, together with the appendix, is the utmost frequent site of enterolithiasis, while in the small intestine, the terminal ileum is the most common location. Here, an alkaline pH encourages the precipitation of calcium salts around food particles, forming a nidus. The increasing incidence of enterolithiasis is attributed to advancements in radiological imaging (5).
It is important to note that tuberculosis as a reason for enterolithiasis is very infrequent (5). Chawla et al. reported out of 400 cases of intestinal tuberculosis, enterolithiasis was seen in only 3.25% (10). Enterolithiasis linked to intestinal tuberculosis is higher in women, which may be due to the higher incidence of intestinal Koch’s in women (11). In the present case, tubercular strictures create a favorable environment for stone formation. Enteroliths can be asymptomatic or may cause intestinal obstruction if they become impacted. They have also been known to provide clues to underlying intestinal pathology (11). Radiographic findings of enteroliths showed an association with the calcium percentage of the stone. The key radiological signs include a dense rim with a pale core, round, oval, or rectangular shadows, a “coin-end-on” look, and wide mobility of the radio-opaque shadows in comparison to fixed structures across consecutive plain radiographs(5). A CT scan can help identify the underlying intestinal pathology that contributes to stone formation(4). Treatment of enterolithiasis involves stone removal and addressing the underlying causes to prevent recurrence. Small stones (<2 cm) that do not cause luminal compromise may pass with conservative management, while larger stones generally require intervention. Treatment options include endoscopic dilation, stone retrieval, or lithotripsy. In severe cases, surgical procedures such as digital fragmentation, enterotomy, or bowel resection may be necessary (4).

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Conclusion

Enterolithiasis, although uncommon, should be considered in the variance diagnosis of small bowel obstruction, particularly in patients with a history of intestinal tuberculosis. This case emphasizes the importance of recognizing enterolithiasis as a potential complication in such patients. Early diagnosis, supported by appropriate imaging modalities, and prompt surgical intervention, along with anti-tubercular therapy, are essential for optimizing patient outcomes. This case emphasizes the need for clinicians to be vigilant about rare causes of obstruction, thereby ensuring timely and effective management.

Acknowledgement
I would like to thank my patient and her family members for cooperating throughout the follow-up and giving consent to publish her case.

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Authors’ Contributions
MLP led in conceptualization and data curation. GTP led in methodology. All authors equally contributed in resources, investigation, supervision and in writing, reviewing & editing of the original draft.

 

References

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