Case of anisakiasis presenting as an Amyand hernia

Abstract

This is a case of a 31-year-old male patient who presented with signs and symptoms of an incarcerated inguinal hernia. The patient’s preoperative imaging showed a tubular structure in the inguinal canal and given the patient’s history at presentation, there was a concern for herniation of the appendix, known as an Amyand hernia. On laparoscopy, there was no evidence of appendiceal involvement and a standard open inguinal hernia was completed. On the final pathology of the hernia sac, roundworms were identified with Y-shaped lateral cords suggesting infection by Anisakis spp. On a further interview with the patient, he revealed that he had recently travelled to Alaska and had consumed raw salmon on a fishing trip. This case demonstrates the importance of a thorough social and travel history. One should also have a low threshold to broaden the differential diagnosis when medical work-up deviates from the standard course.

Case presentation

This is a 31-year-old man presenting with 3 days of worsening right groin pain associated with mild nausea. The patient denied fevers, chills or changes in bowel movements at the time of presentation. The patient had a known right inguinal hernia that would occasionally become symptomatic. On examination at presentation, the patient had signs of an incarcerated right inguinal hernia with significant tenderness to palpation. Preoperative vital signs were within normal limits. The patient’s white cell count was 8.8×10⁹/L, eosinophil ratio was normal at 3.9%, electrolytes were within normal limits and urinalysis was negative. Diagnostic CT scan of the abdomen and pelvis revealed an incarcerated right inguinal hernia with a tubular structure with significant inflammation around it (figure 1). At that time, history, physical examination and imaging were concerning for Amyand hernia.

Figure 1.

Representative cross-sectional imaging showing a tubular structure within the hernia space.

Treatment

The patient was taken to the operating room for a laparoscopic appendectomy and possible right inguinal hernia repair. During laparoscopy, a small direct right inguinal hernia was visualised. The appendix was noted to be normal and the planned appendectomy was performed. The patient was re-prepped and draped for an open right inguinal hernia repair. A standard open inguinal hernia dissection was performed. The spermatic cord was noted to be very adherent to the internal oblique fascia on blunt dissection. The spermatic cord was also noted to be thickened within an increased amount of fluid in the area. A tubular structure was noted anterior medially to the spermatic cord, which was believed to be hernia sac. This dissected directly off the pampiniform plexus and vas deferens to the internal inguinal ring proximally. This tissue was noted to be a fibrous band without patency and was therefore amputated at the internal inguinal ring and sent for pathology. No further hernia sacs were noted and a Shouldice-type repair was performed.

Outcome and follow-up

Histologic evaluation of the appendix showed fibrous obliteration of the lumen with no evidence of appendicitis. The hernia sac demonstrated abscess with numerous eosinophils, and in the cross-section profile, roundworms were identified. These lacked the typical peripheral alae common to Enterobius vermicularis, instead, the cross-sections demonstrated Y-shaped lateral cords suggesting infection by Anisakis spp (figure 2). During postoperative follow-up, further history was taken and the patient disclosed that 2 weeks prior to surgery he had been on a trip to Alaska and ate raw salmon directly from a stream. The patient was successfully treated with the appropriate anti-parasitic medications in the outpatient setting and there were no complications in the patient’s recovery.

Figure 2.

Cross-section of Anisakis with surrounding inflammation at 100× magnification.

Discussion

Amyand’s hernia is named after the English surgeon Claudius Amyand, who performed the first successful appendectomy. It is a rare form of hernia in which the vermiform appendix protrudes into the hernia sac, accounting for less than 1% of hernia cases.¹ It usually presents in a clinical picture similar to that of a strangulated hernia. Amyand’s hernias are quite rare but it is even more rare to have hernia associated with parasitic infection.

There are very few cases of parasitic infections within surgical pathology specimens reported in the literature, most of which are single case reports predominantly in the Asian and Latin American literature where these infections are more endemic. To our knowledge, this is the first reported case of anisakiasis reported within an inguinal hernia. Wu and colleagues report a case of Schistosoma japonicum within an inguinal hernia sac. In contrast, this was believed to be due to chronic infection secondary to consumption of infected river water at an early age rather than an acute infection as in this case.²

Anisakiasis is the human disease caused by the accidental ingestion of the larval nematodes Anisakis or Pseudoterranova. The third stage larva of Anisakis spp can infect a wide range of fish and mollusks and consumption of undercooked seafood in the form of sushi, ceviche or improper processing can lead to anisakiasis. Larvae are killed by heating seafood to 60°C for 1 min or freezing to −20°C for 24 hours. Gastric anisakiasis usually presents in the first 1–7 hours and intestinal anisakiasis manifests 5–7 days following consumption. Both forms present with severe epigastric or abdominal pain, nausea and vomiting. Infected patients exhibit mild elevation of temperatures, moderate leucocytosis (10 000–15 000 leucocyte per 10⁹/L) and varied eosinophil counts (4%–41%). Patients with intestinal anisakiasis are misdiagnosed as acute appendicitis greater than 50% of the time. Infection is also associated with a strong allergic response, including swelling, urticaria and anaphylactic shock.^{3 4}

Anisakiasis occurs throughout the world, with around 20 000 reported cases to date, with 90% of cases occurring in Japan. The increasing global demand for seafood and a growing preference for raw fish have increased the risk of anisakiasis and other fish-borne parasitic zoonoses in the western world.⁵ Fish dishes that are considered high-risk include marinated anchovies, ceviche, salted herring, sushi and sashimi.⁴

On histologic section, Anisakis is identified by distinctive Y-shaped lateral cords, a lack of lateral alae extending from the cuticle, and 60–90 muscle cells per quadrant. In acute infection, tissues show infiltration of neutrophils with little oedema. Within the first week, massive eosinophilic infiltration occurs with oedema of the submucosa. In chronic cases, necrosis, haemorrhage and abscess formation can occur.^{3 4}

The patient’s symptoms of abdominal pain and nausea beginning 1 week after consumption of raw fish are typical to the clinical picture of intestinal infection with anisakiasis. This was complicated by the patient’s history of prior inguinal hernia. On original examination, the possibility of this diagnosis was missed due to the patient’s history of a direct inguinal hernia, which was confirmed by CT imaging showing a tubular structure. This led to the preoperative diagnosis of Amyand hernia and appendicitis. Although Amyand hernia is rare, it is much more likely in a patient with a negative travel history which was not elicited from the patient during preoperative evaluation. A more thorough travel and social history in the preoperative period could have revealed the possibility of this hernia being complicated by a parasitic infection instead of appendicitis and Amyand hernia.

Patient’s perspective.

I learnt medication is 17.5 times more expensive in the USA than Canada. The cost for 2 weeks of albendazole at that time was $1400 in the USA and $80 in Canada. I also became concerned about sushi, but came to learn that sushi in the USA is flash frozen to make it safer to consume.

Learning points.

• Surgical problems are common, but always keep a low threshold to evaluate for an alternate diagnosis when the work-up deviates from the norm.

• It is crucial to take a full history and physical of any patient presenting with an acute problem, as the diagnosis can almost always be drawn from a thorough history and physical.

• When patients who have consumed raw seafood or have significant travel history present with abdominal pain, nausea and vomiting, a diagnosis of anasakiasis or other parasitic infection should be considered