Radiographic diagnosis of equine enterolithiasis associated with the presence of an enterolith with a metallic nidus (nail)

Abstract

Enteroliths are formed by the deposition of concentric bands of minerals around a central core, such as stones or plastic, ingested intentionally or accidentally. The ingestion of metallic and perforating foreign bodies is uncommon in equine medicine. However, when such ingestion does occur, it can predispose patients to episodes of colic and peritonitis, in addition to the formation of abscesses. These objects are normally only detected during celiotomy, but, early diagnosis is important in the search for better patient prognosis. In this report, we described a case of equine enterolithiasis with the presence of a metallic nidus (nail) in one of the enteroliths, that was diagnosed using abdominal radiography, and confirmed surgically.

Alternate abstract:

Os enterólitos são formados por faixas concêntricas em torno de um núcleo central, que podem ser ingeridos propositalmente ou acidentalmente, como pedras e plástico. A ingestão de corpos estranhos metálicos e perfurantes não são comuns na medicina equina e, quando ocorrem, podem predispor a episódios de cólicas e peritonites, além da formação de abscessos. A detecção desses achados normalmente é realizada durante a celiotomia, porém o diagnóstico precoce é um ponto importante na busca de um melhor prognóstico para o paciente. O objetivo deste relato foi descrever um caso de enterolitíase equina com presença de nicho metálico (prego) em um dos enterólitos, diagnosticado com auxílio de radiografia abdominal e confirmado cirurgicamente.

Enteroliths are intestinal calculi formed by the deposition of struvite, magnesium, and ammonia (SOUTHWOOD, 2019), in addition to other substances such as sodium, potassium, calcium, and sulfur (PIERCE, 2009), as well as several minerals formed in the large intestine of horses. These components accumulate around a nucleus, which generally comprises an object ingested intentionally or accidentally and are not digested, such as stone, plastic, horsehair, nylon threads, and rope halters (SOUTHWOOD, 2019). Unlike in ruminants, the ingestion of metallic foreign bodies is uncommon in horses; however, when this does occur, the ingested objects can predispose horses to episodes of colic and peritonitis, in addition to abscess formation.

A definitive diagnosis of enterolithiasis is usually made surgically; however, abdominal radiography is an option that may allow the presurgical diagnosis of enteroliths and metallic foreign bodies.

The present report described a case of equine enterolithiasis with the presence of a metallic nucleus (nail) in one of the enteroliths, which was diagnosed using abdominal radiography and confirmed surgically.

Clinical case report

A 14-year-old castrated male equine of the Brazilian Equestrian breed with a history of intermittent abdominal pain was brought to the Guadalupe Veterinary Clinic for abdominal radiography. In addition to a history of intermittent abdominal pain, the animal also had parorexia and coprophagia. The patient remained mostly under confinement, with a diet comprising alfalfa, commercial feed, and oats. Upon arrival at the clinic, the patient underwent radiographic examination using the MAG DYNAMIC C 500Ma/150 Kv model equipment. An image suggestive of enterolithiasis was verified in the laterolateral projection (125 kV and 20mAs), with one of the enteroliths shown to contain a metallic nucleus (nail) (Figure 1). The horse did not experience abdominal pain, while clinical and hematological examinations (hemograms) were unchanged. Based on the imaging findings, the patient was referred for a median celiotomy.

The anesthetic protocol comprised butorphanol (0.04 mg/kg, IV) and detomidine (0.02 mg/kg, IV) as pre-anesthetic medication, in addition to the administration of flunixin meglumine (1.1 mg/kg, IV). Anesthetic induction was performed with diazepam (0.05 mg/kg, IV) and ketamine (2.5 mg/kg, IV), while maintenance included isoflurane and infusion with lidocaine (3 mg/kg/h, IV), xylazine (0.7 mg/kg/h, IV) and ketamine (0.6 mg/kg/h, IV). The abdominal cavity was accessed through a ventral midline celiotomy and, following inspection of the abdomen, the large colon was exteriorized, and several enteroliths were observed within its lumen. Pelvic flexure enterotomy was performed to lavage the colon and remove enteroliths. At least 39 enteroliths were identified (Figure 2), some of which were small and were not counted. Because it was not possible to determine the enterolith containing the foreign body of the nail, radiographs were taken during the removal of the enteroliths to verify a metallic nucleus, which was ultimately identified in one of the enteroliths (Figure 3). Enteroliths with metallic nuclei and concretions with a core formed by a string-like structure were observed (Figure 4). Most of the removed enteroliths were concentrated in the right dorsal colon.

Enterorrhaphy was performed with a double invaginating pattern using the Schmieden followed by Cushing, with polydioxanone No. 2-0 sutures. Subsequently, a second inspection of the gastrointestinal tract and abdominal cavity was performed, the viscera were repositioned, and celiorrhaphy was performed. The linea alba was sutured in a simple continuous pattern using polydioxanone No. 4, subcutaneous tissue No. 0, and skin No. 1 sutures.

After recovery from anesthesia, which proceeded uneventfully, postoperative support was administered, comprising administration of fluid therapy comprising ringer lactate supplemented with lidocaine, calcium and potassium chloride during the first 2 days, broad-spectrum antibiotic therapy with gentamicin (6.6 mg/kg/SID/IV) and procaine benzylpenicillin (20,000 IU/kg/BID/IM), both for ten days, with metronidazole (15 mg/kg/BID/PO) during the first 5 days, flunixin meglumine (1.1 mg/kg/BID/IV) for 5 consecutive days and then SID until the tenth day after the procedure.

The surgical wound was cleaned using saline solution and chlorhexidine three times a day. Walking and grazing were performed at least once a day. On the tenth postoperative day, the stitches were removed, and the patient was discharged.

The collected intestinal concretions were weighed yielding a total weight of 644.9 g, and an average weight of 71.6 g, with the largest enterolith weighing 72 g. A 10% sample of the stones was sent for qualitative analysis, which revealed the presence of carbonate, oxalate, phosphate, magnesium, and ammonia.

In the history of horses with suspected enterolithiasis, factors such as stall confinement, feeding with alfalfa, habit of eating unusual objects, and history of episodes of intermittent abdominal pain have been shown to be clinically suspicious (SOUTHWOOD, 2019). In the present case, the horse owner’s report of parorexia, defined as the habit of ingesting non-nutritive foods such as ropes, plastic, nylon thread, and rope halters, aided in the diagnosis. This habit may be purposeful, as in the case described, or it may occur due to accidental ingestion (SOUTHWOOD, 2019).

The ingestion of metallic foreign bodies; although uncommon in horses, has been reported as the cause of acute abdomen in this species (GÓSS et al., 2019). In the present case, a nail served as the central nucleus of one of the enteroliths that caused the clinical characteristics evidenced in the anamnesis.

Other important observations made during the anamnesis of the horse included prolonged stabling and alfalfa feeding. The qualitative evaluation of enteroliths verified the presence of minerals that may be linked to this animal’s diet. Alfalfa alkalizes the intestinal pH, resulting in the incomplete digestion of some minerals, as well as for struvite precipitation and deposition of these minerals around a nucleus (HASSEL et al., 2004). In a study by HASSEL et al. (2004), the average pH of the colonic contents of horses with enterolithiasis was found to be significantly higher than that of horses in the control group. ROUFF et al. (2018) and HASSEL et al. (2004) previously described alfalfa reeding as a risk factor for the development of enterolithiasis, but reinforced that it cannot be considered in isolation, as many animals that have an alfalfa-based diet do not develop the condition. Other factors that can regulate colonic pH included the bacterial microbiota, genetic factors, innate deficiency in colonic mechanisms for ion exchange, and the pH of the water ingested by the animal.

Intestinal hypomotility, absence or reduction of defecation, soft stools, distension and abdominal pain are among the clinical signs of obstructive colic syndrome that may aid in the diagnosis of enterolithiasis (SOUTHWOOD, 2015). When the present animal was treated, it did not exhibit colic symptoms; however, recurrent abdominal pain contributed to the diagnosis.

A definitive diagnosis of enterolithiasis is possible only through exploratory celiotomy, abdominal radiography, or necropsy (PIERCE, 2009). As such, abdominal digital radiography is an important diagnostic method for enterolithiasis, with greater sensitivity and specificity for enteroliths present in the large colon, but reduced sensitivity for enteroliths in the small colon. Possible limiting factors of this technique include insufficient radiation penetration into the abdomen (KELLEHER et al., 2014), location of the enterolith, and abdominal gas distention (SOUTHWOOD, 2019). In the present study, a sugestive image of enterolithiasis was identified, with concretions present mainly in the right dorsal colon, with one of the possible enteroliths associated with a metallic core (nail).

Horses with a compatible history can undergo abdominal radiographic examination without presenting with a clinical condition of abdominal pain, which is referred to as celiotomy, and without the hemodynamic changes expected during an obstructive condition. Injuries can be prevented by intramural vascular compression and occlusion of the local arterial supply, which can lead to ischemia and necrosis of the affected intestinal segment, in cases of enteroliths or fecalomas during prolonged obstructive colic syndrome (COOK et al., 2019), thus contributing to a better postoperative prognosis.

Although, the presence of metallic objects in the intestinal lumen is rare, abdominal radiography remains an important tool for diagnosing these objects, which can predispose to the occurrence of abscesses, perforations, and peritonitis (HASSEL, 2001). Early and accurate diagnosis through abdominal radiography can save resources related to time and money, by avoiding the provision of useless conservative treatments for obstructive colic syndrome, such as fluid therapy and laxatives, and allowing the patient to undergo celiotomy directly. In the present report, the animal was referred for radiographic examination because of its medical history, and not because it was experiencing pain because of obstruction. Thus, corroborating previous reports in the literature, the present horse showed an uneventful recovery after the surgical removal.

Median celiotomy is the treatment of choice for enterolithiasis, with enteroliths removed through one or more enterotomies, as necessary. However, necrosis and intestinal rupture can occur because of delayed diagnosis, impairing prognosis and possibly leading to death (SOUTHWOOD, 2015). In the present study, surgical intervention was performed without any circulatory alterations.

Due to the possibility of enterolithiasis recurrence, it is recommended that animals with a history of this condition change daily management, such as observing objects that could be ingested, reducing alfalfa consumption, and reducing stabilization time (SOUTHWOOD, 2019).

Although, abdominal radiography is a common complementary examination for horses with colic in other countries, its use in Brazil remains restricted. However, enterolithiasis is a highly prevalent condition in the south of the country, and even though the ingestion of metallic foreign bodies is uncommon in equine species, stable animals can acquire stereotypies and compromise their health, as seen in the case described. This case highlighted the importance of performing radiographic evaluation in cases of enterolithiasis, which can visualize the enteroliths and metallic objects, in addition to carrying out an early diagnosis, favoring the occurrence of a better prognosis.

ACKNOWLEDGEMENTS

This paper was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brasil - Finance code 001.

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