Acute invasive small-bowel Anisakiasis: clinical and CT findings in 19 patients

Anisakidae and Anisakidosis: A Public Health Perspective

Fish and seafood are increasingly recognised as safe and nutritiously valuable foods of animal origin, being a source of about 17% of animal protein globally. Novel culinary trends encourage the consumption of raw or thermally lightly processed fishery products. At the same time, consumers prefer wild, fresh and whole fish over farmed or processed fish. However, the consumption of raw or undercooked fish and other marine organisms poses a risk of contracting parasitic infections, potentially representing a public health risk. Among the most common seafoodborne parasites are members of the Anisakidae family, especially the genus Anisakis, which can cause potentially detrimental effects to human health. These parasites are the causative agent of a zoonosis termed anisakidosis that is prevalent in countries with high per capita fish consumption. Although the number of annual clinical cases varies among countries and regions and is generally not high, sensitisation to this parasite in the general population seems to be considerably higher. Therefore, anisakidosis is still significantly underreported and misdiagnosed globally, making it a disease of rising public health concerns. To prevent infection and mitigate potential negative effects on human health, proper preventive measures such as gutting the fish, freezing or thermal processing are needed. Moreover, a holistic approach implementing One Health principles together with educational campaigns towards the general public and primary care physicians can extend the knowledge on the occurrence of these parasites in their natural hosts and the diagnosis and incidence of anisakidosis, with a final goal to minimize risks for human health and reducing costs for health systems.

First Case of Human Anisakiosis in Greece: Acute Invasive Infection Mimicking Peritoneal Malignancy

Consumption of raw and mildly processed seafood, in the context of modern Western world eating trends, is recognized as a major driver for human fish-borne infections. However, these zoonoses and their unfamiliar risks remain neglected and underappreciated among European diagnosticians. In contemporary Europe anisakidosis is one of the most important fish-borne zoonoses. It is caused by ingesting the third-stage infective larvae of the nematode parasites that belong to the family Anisakidae. The case described herein, is an intestinal and ectopic form of anisakiosis (Anisakis spp.), causing symptoms of subacute abdomen and masquerading as an intraperitoneal malignancy. It is the first anisakidosis case reported in Greece, affecting a young patient who had been repeatedly exposed to the parasite by consuming homemade raw fish. Right hemicolectomy, omentectomy and excision of a descending colon nodule were uneventfully performed. The pathology report confirmed granulomatous tissue with eosinophilic infiltration and parasites that were morphologically and molecularly identified as Anisakis spp. Although challenging, acquiring an accurate diagnosis of anisakidosis can prevent unnecessary surgery, as the infection typically is self-resolving, and if treatment is deemed necessary, it can be limited to antiparasitic medication. However, in rare cases, extra-gastrointestinal migration of larvae can cause severe damage with practically unknown risks, posing a diagnostic and therapeutic dilemma. In such a clinical case scenario, surgical exploration can decisively contribute to a definitive diagnosis and early identification of intraabdominal complications necessitating surgical intervention.

Evaluation of imaging findings in gastrointestinal anisakiasis in emergency CT and ultrasound

BACKGROUND

To assess the frequency of appearance of various signs (isolated and grouped) in emergency imaging tests in patients with anisakiasis, according to the location of gastrointestinal tract involvement.

METHODS

Retrospective review by two experienced radiologists of emergency ultrasounds and CTs performed on patients admitted in the Emergency Department of our hospital with later confirmed anisakiasis (2010-2021), assessing the presence of signs suggesting anisakiasis. Calculation of the frequency of appearance according to the gastric or intestinal location, as well as the most common grouped signs.

RESULTS

Out of 231 total patients with anisakiasis, imaging studies were performed in 144: abdominopelvic ultrasound in 43 cases and CT in 111 (both techniques in 31). In cases with gastric occurrence (34), in CT the wall stratification (100%), wall thickening (97%), fat stranding (91%) and ascitic fluid (82%) were predominant. In the intestinal cases (105), in CT (95) the wall thickening (100%), fat stranding (92%) and mesenteric vessel engorgement (83%) were usual; in ultrasound (40), ascitic fluid and wall thickening (70% in both cases) were frequently observed. The frequency of grouped appearance of the mentioned signs was 82% in gastric cases, 80% in intestinal cases and 50% in ultrasounds. Multisegment involvement in CT reached 28% (gastric + intestinal) and 11% (only intestinal) of cases.

CONCLUSIONS

The most frequent CT findings in patients with gastric anisakiasis are wall stratification and thickening, fat stranding and ascitic fluid. In the intestinal cases, wall thickening, fat oedema and vessel engorgement are the most often observed findings.

CRITICAL RELEVANCE STATEMENT

The presence of different radiological signs makes it advisable to include anisakiasis in the differential diagnosis of acute abdomen. Intestinal and multifocal involvement rates are greater than previously reported.

KEY POINTS

• In gastric anisakiasis, CT frequently shows wall stratification and thickening, fat stranding and ascitic fluid. • In intestinal anisakiasis, CT often presents wall thickening, fat stranding and vessel engorgement. • In intestinal anisakiasis, ultrasounds most frequently show ascitic fluid and wall thickening.

Intestinal anisakiasis: CT imaging findings-a 10-year descriptive study in a single center

PURPOSE

The aim of this study was to retrospectively review cases of intestinal anisakiasis diagnosed by CT over a 10-year period and to evaluate imaging findings associated with the disease.

METHODS

This retrospective study included 71 patients with clinical suspicion of intestinal anisakiasis in whom an abdominopelvic computed tomography (CT) was performed at a single institution between June 2011 and December 2021. To identify the cases, we used medical term search engines and the hospital's radiology case database. Clinical information was gathered from the medical records. A radiologist with five years of experience reviewed and analyzed the CT images to determine the characteristic findings of intestinal anisakiasis.

RESULTS

The study included 47 confirmed cases of intestinal anisakiasis. The mean age of the patients was 52 years (range 18-87 years), being more frequent in men than women (26:21). All patients reported ingestion of raw fish, most commonly anchovies in vinegar (30/47, 63,8%). Abdominal pain was the predominant symptom, accompanied by nausea, vomiting, and occasionally fever. The most common clinical suspicions were intestinal obstruction (14/47, 29,8%) and appendicitis (10/47, 21,3%), whereas intestinal anisakiasis was suspected in only 2 cases prior to imaging. CT showed thickening of the bowel wall with submucosal edema in all patients, predominantly involving the ileum (43/47, 91,5%), usually in a relatively long segment (mean of 17,5 cm, range 10-30 cm). Simultaneous involvement of multiple bowel segments was observed in 16 cases (34%). Intestinal obstruction with dilatation of proximal loops (33/47, 70,2%), ascites (45/47, 95,7%), and mesenteric fat striation (32/47, 68,1%) were also common findings.

CONCLUSION

This study demonstrates the value of computed tomography in suggesting the diagnosis of intestinal anisakiasis, which often presents with nonspecific clinical manifestations. The characteristic CT findings that provide diagnostic clues are bowel wall thickening with submucosal edema, typically involving a long segment of the ileum, with signs of intestinal obstruction, ascites, and mesenteric fat striation. Simultaneous involvement of several intestinal segments (typically the gastric antrum and right colon) is an additional finding to be considered and may provide a diagnostic clue.

Anisakiasis: Imaging findings

OBJECTIVE

To review the main findings for anisakiasis in the different imaging tests that can be used to diagnose it, based on studies done at our center.

CONCLUSION

The presence of Anisakis species in food consumed in Western countries is becoming more common. Patients with anisakiasis present with acute abdomen; there are no specific clinical signs or laboratory findings. Careful history taking is key to discovering exposure to Anisakis-contaminated food, but this task is hindered by unfamiliarity with the condition and lack of suspicion and is also confounded by the variable latency period after ingestion of Anisakis-contaminated food. Give the nonspecific presentation, patients with anisakiasis often undergo imaging tests to rule out other processes. Thus, radiologists need to be familiar with the spectrum of imaging findings that should lead to the inclusion of anisakiasis in the differential diagnosis, so they can guide clinicians toward directed history taking and specific tests.

Diagnostic approach to small-bowel wall thickening: Beyond Crohn's disease and cancer

Although small-bowel wall thickening is a common manifestation of Crohn's disease and tumors, many other entities can give rise to similar imaging findings. The small bowel is difficult to access by endoscopy, so radiologic imaging tests play an essential role in the diagnosis of conditions involving the small bowel. The main objectives of this paper are to explain the definition of small-bowel wall thickening, analyze the patterns of involvement seen in multidetector computed tomography (MDCT) with intravenous contrast administration, and provide an image-based review of the different causes of small-bowel wall thickening. The differential diagnosis must include many entities because wall thickening can result from immune-mediated, infectious, or vascular causes, as well as from toxicity and other lesser-known entities. As the imaging appearance of many of these conditions overlap, clinical and laboratory findings are necessary to support the imaging diagnosis.

Anisakiasis of the Terminal Ileum Removed by Colonoscopy

A 35-year-old Japanese man with no significant medical history presented to the emergency department complaining of abdominal pain, nausea, and vomiting 35 h after ingesting raw horse mackerel, sardines, and tuna. Computed tomography of the abdomen with intravenous contrast revealed significant thickening of the terminal ileum with mild proximal dilatation and moderate ascites. On colonoscopy, an actively moving anisakis larva was discovered in the terminal ileum. The larva was removed with endoscopic forceps. The patient's symptoms resolved quickly following the procedure.

Diagnostic approach to small-bowel wall thickening: beyond Crohn's disease and cancer

Although small-bowel wall thickening is a common manifestation of Crohn's disease and tumors, many other entities can give rise to similar imaging findings. The small bowel is difficult to access by endoscopy, so radiologic imaging tests play an essential role in the diagnosis of conditions involving the small bowel. The main objectives of this paper are to explain the definition of small-bowel wall thickening, analyze the patterns of involvement seen in multidetector computed tomography (MDCT) with intravenous contrast administration, and provide an image-based review of the different causes of small-bowel wall thickening. The differential diagnosis must include many entities because wall thickening can result from immune-mediated, infectious, or vascular causes, as well as from toxicity and other lesser-known entities. As the imaging appearance of many of these conditions overlap, clinical and laboratory findings are necessary to support the imaging diagnosis.

Usefulness of Ultrasound in the Diagnosis of Intestinal Anisakiasis

OBJECTIVES

To evaluate the ultrasound (US) findings of gastrointestinal anisakiasis and the utility of US in its early diagnosis.

METHODS

We retrospectively assessed the imaging findings and clinical data of 21 patients with gastrointestinal anisakiasis. Diagnosis was confirmed by a positive antigen (n = 16), endoscopy (n = 2), or a compatible clinical presentation, physical examination, and history of raw fish consumption (n = 3). Ultrasound findings reviewed included segmental circumferential bowel wall thickening, segmental edema of the valvulae conniventes, dilated small bowel loops with hyperperistalsis or hypoperistalsis, free fluid, and color Doppler hyperemia.

RESULTS

Segmental circumferential bowel wall thickening was present in all 21 patients, whereas segmental edema of the valvulae conniventes was visualized in 13 patients, moderately dilated small-bowel loops proximal to the affected segment with increased peristalsis in 14 patients, small-to-moderate ascites in 18 patients, and color Doppler hyperemia in 7 patients. The US evaluation ruled out a surgical pathologic examination in all patients, and the diagnosis of anisakiasis was suggested by the radiologist on the basis of US findings in 12 patients.

CONCLUSIONS

Familiarity with the suggestive US presentation of intestinal anisakiasis may allow the radiologist to propose the diagnosis of this overlooked cause of abdominal pain and may also prompt an investigation of recent raw or lightly cooked seafood ingestion. Ultrasound findings of bowel wall thickening, especially segmental edema of the valvulae conniventes, hyperperistalsis, and dilatation of small-bowel loops proximal to the affected segment, ascites, and color Doppler hyperemia, along with a history of raw fish ingestion should aid the radiologist in the diagnosis of anisakiasis.

Common Symptoms from an Uncommon Infection: Gastrointestinal Anisakiasis

Clinicians can be forgiven for thinking of anisakiasis as a rare condition low in the differential diagnosis of abdominal pain. Gastrointestinal anisakiasis is a zoonotic parasitic disease caused by consumption of raw or undercooked seafood infected with nematodes of the genus Anisakis. Even though the reported cases indicate that this is a rare disease, the true incidence of the disease could be potentially higher than what is reported in the literature as cases can go undiagnosed. Diagnosis and treatment of gastric anisakiasis are made by a compatible dietary history, direct visualization, and removal of the larvae via gastroscopy. Serologic testing and imaging studies are useful in the diagnosis of intestinal anisakiasis and conservative management should be considered. This disease may mimic other diseases and lead to unnecessary surgery. This emphasizes the importance of suspecting gastrointestinal anisakiasis by history taking and by other diagnostic modalities.

Anisakiasis: Report of 15 Gastric Cases Caused by Anisakis Type I Larvae and a Brief Review of Korean Anisakiasis Cases

The present study was performed to report 15 anisakiasis cases in Korea and to review the Korean cases reported in the literature. Total 32 Anisakis type I larvae were detected in the stomach of 15 patients by the endoscopy. Single worm was detected from 12 cases, and even 9 larvae were found from 2 cases. Epigastric pain was most commonly manifested in almost all cases, and hemoptysis and hematemesis were seen in 1 case each. Symptom manifestations began at 10-12 hr after eating fish in 73.3% cases. Endoscopy was performed 1-2 days after the symptom onset in most cases. The common conger, Conger myriaster, was the probable infection source in 7 cases. In the review of Korean anisakiasis cases, thus far, total 645 cases have been reported in 64 articles. Anisakis type I larva was the most frequently detected (81.3%). The favorable infection site of larvae was the stomach (82.4%). The common conger was the most probable source of human infections (38.6%). Among the total 404 cases which revealed the age and sex of patients, 185 (45.8%) were males, and the remaining 219 (54.2%) were female patients. The age prevalence was the highest in forties (34.7%). The seasonal prevalence was highest in winter (38.8%). By the present study, 15 cases of gastric anisakiasis are added as Korean cases, and some epidemiological characteristics of Korean anisakiasis were clarified.