Linear Foreign Bodies

Linear foreign bodies (LFB) are elongated, pliable objects (e.g., strings, threads, yarn, fabric strips, fishing line, ribbon, tinsel) that are ingested by animals and become anchored at a proximal point in the gastrointestinal tract (typically the base of the tongue, pylorus, or proximal duodenum) while the distal portion is propelled aborally by peristalsis. This creates a characteristic plication or accordion-like bunching of the intestines along the foreign body, leading to partial or complete intestinal obstruction, serosal abrasion, and potentially intestinal perforation, peritonitis, and sepsis. The condition is most common in cats but also occurs in dogs, especially young individuals. Surgical management is often required, involving enterotomy or resection and anastomosis, and carries a good prognosis if diagnosed early.

The primary etiology is the ingestion of a linear object. Common items include sewing thread, dental floss, yarn, string, ribbon, tinsel, fabric strips, fishing line, and even linear pieces of rubber or plastic. The object typically becomes anchored at a fixed point, such as the frenulum of the tongue, the pylorus, or the ileocecal valve. The anchoring prevents complete passage, while peristalsis continues to pull the distal end, causing the intestines to bunch up (plicate) along the foreign body. This plication leads to mechanical obstruction, ischemia of the intestinal wall due to compression and tension, and eventually necrosis and perforation if not relieved. In some cases, the foreign body may also cause intussusception. The condition is often associated with pica or behavioral issues, especially in young animals or those with access to sewing materials or toys.

Linear foreign bodies are most commonly reported in cats, particularly young cats (less than 2 years old) and those with access to string, yarn, or thread. Dogs are also affected, with a higher incidence in young, active breeds that are prone to chewing and ingesting non-food items. There is no strong breed or sex predisposition, but Siamese and other oriental cat breeds may be overrepresented due to their curious and playful nature. The condition is seen worldwide and accounts for a significant proportion of gastrointestinal foreign body cases in small animal practice. In one study, linear foreign bodies represented approximately 10-20% of all gastrointestinal foreign bodies in cats. The incidence may be higher in households where sewing, knitting, or crafting is common, and during holiday seasons when tinsel and ribbon are available.

The pathophysiology of linear foreign bodies involves a cascade of mechanical and ischemic events. Initially, the foreign body is ingested and becomes anchored at a proximal site, often the base of the tongue (under the frenulum) or the pylorus. The distal portion continues to move aborally due to peristalsis, but because the proximal end is fixed, the intestine is pulled and bunched into accordion-like folds (plication). This plication causes partial luminal obstruction, leading to accumulation of fluid and gas proximal to the obstruction, resulting in vomiting and dehydration. The tension on the mesenteric border of the intestine compromises blood flow, leading to ischemia, necrosis, and eventually perforation. The foreign body may also cause direct mechanical abrasion of the mucosa, leading to ulceration and bacterial translocation. If perforation occurs, septic peritonitis develops rapidly, causing systemic inflammatory response syndrome (SIRS), sepsis, and potentially death. In some cases, the foreign body may become embedded in the intestinal wall, leading to localized abscessation or granuloma formation.

Intrinsic factors include young age (curiosity and exploratory behavior), pica (a tendency to eat non-food items), and certain behavioral traits such as anxiety or boredom. Cats, especially those kept indoors, are at higher risk due to exposure to household items like thread, yarn, and tinsel. Dogs, particularly working breeds or those with high prey drive, may ingest linear objects while playing. Extrinsic factors include environmental availability of linear objects, such as sewing kits, craft supplies, fishing gear, and holiday decorations. Poor supervision and inadequate environmental enrichment can increase the risk. Additionally, animals with a history of previous foreign body ingestion or gastrointestinal surgery may have altered motility or adhesions that predispose to recurrence.

Clinical signs of linear foreign bodies are often progressive and may include: 1) Vomiting (often intermittent, progressing to frequent and severe), 2) Anorexia or decreased appetite, 3) Lethargy and depression, 4) Abdominal pain (manifested as restlessness, vocalization, or guarding of the abdomen), 5) Diarrhea or tenesmus (if the foreign body is partially passed), 6) Dehydration and electrolyte imbalances due to vomiting, 7) Fever (if peritonitis develops), 8) Palpable abdominal mass or plicated intestines on abdominal palpation, 9) In cats, the foreign body may be visible under the tongue (e.g., string wrapped around the base of the tongue). In advanced cases, signs of septic shock (tachycardia, weak pulses, pale mucous membranes, hypothermia) may be present. Physical examination may reveal a painful abdomen, and in some cases, the foreign body may be felt per rectum if it has passed into the colon.

Differential diagnoses for linear foreign bodies include: 1) Other gastrointestinal foreign bodies (non-linear, such as toys, bones, or masses), 2) Intussusception, 3) Gastroenteritis (infectious, dietary, or inflammatory), 4) Pancreatitis, 5) Intestinal neoplasia (e.g., lymphoma, adenocarcinoma), 6) Inflammatory bowel disease, 7) Parasitic infections (e.g., roundworms, hookworms), 8) Metabolic diseases causing vomiting (e.g., renal failure, hepatic disease, diabetic ketoacidosis), 9) Peritonitis (septic or sterile), 10) Obstruction due to stricture or adhesion. Key differentiating features include history of ingestion, presence of plication on imaging, and identification of the foreign body on palpation or imaging. Intussusception may also cause plication-like appearance but typically has a target-like mass on ultrasound. Gastroenteritis usually lacks obstructive signs and responds to symptomatic treatment. Neoplasia may present with weight loss and chronic signs, and imaging may reveal a mass.

The diagnostic approach for suspected linear foreign body should be systematic: 1) Obtain a thorough history, including possible access to linear objects and onset of clinical signs. 2) Perform a complete physical examination, including oral examination to check for string under the tongue, abdominal palpation to detect plicated intestines or a mass, and rectal examination to feel for the foreign body. 3) Baseline bloodwork (CBC, biochemistry, electrolytes) to assess hydration, electrolyte imbalances, and evidence of inflammation or organ dysfunction. 4) Abdominal radiographs (survey and contrast) are often diagnostic: survey radiographs may show plication of the small intestine (accordion-like bunching), gas patterns suggestive of obstruction, and possibly the foreign body if radiopaque. If survey radiographs are inconclusive, upper gastrointestinal contrast study (barium or iodinated contrast) can demonstrate the foreign body as a linear filling defect and confirm obstruction. 5) Abdominal ultrasound is highly sensitive and can visualize the linear foreign body as a hyperechoic line within the intestinal lumen, with plication and thickening of the intestinal wall. It can also detect free abdominal fluid or peritonitis. 6) If peritonitis is suspected, abdominocentesis or diagnostic peritoneal lavage may be performed to analyze fluid for cytology and culture. 7) In stable patients, advanced imaging (CT) may be used for further characterization, but it is rarely necessary. 8) Exploratory laparotomy is both diagnostic and therapeutic if imaging is inconclusive but clinical suspicion is high.

Laboratory findings in linear foreign bodies are non-specific but may include: 1) Hemoconcentration (elevated PCV) due to dehydration, 2) Leukocytosis with a left shift, or leukopenia in severe sepsis, 3) Elevated liver enzymes (ALT, AST) and bilirubin due to hepatic hypoxia or endotoxemia, 4) Elevated renal parameters (BUN, creatinine) due to prerenal azotemia from dehydration, 5) Electrolyte imbalances: hypokalemia, hyponatremia, hypochloremia due to vomiting, 6) Metabolic alkalosis (from loss of gastric acid) or metabolic acidosis (from lactic acidosis in shock), 7) In peritonitis, abdominal fluid analysis may reveal septic suppurative inflammation (degenerate neutrophils with intracellular bacteria), 8) Blood gas analysis may show acid-base disturbances, 9) Inflammatory biomarkers such as C-reactive protein (CRP) may be elevated. Coagulation panel (PT/aPTT) may be prolonged in sepsis or disseminated intravascular coagulation (DIC).

Radiography: Survey abdominal radiographs may reveal a classic plication or accordion-like bunching of the small intestine, with the foreign body sometimes visible if radiopaque. Gas patterns may indicate obstruction (dilated loops proximal to the obstruction). In cases of perforation, free gas may be seen under the diaphragm. Contrast radiography (upper GI series) can demonstrate a linear filling defect and confirm obstruction, but is less commonly used now due to ultrasound. Ultrasonography: Abdominal ultrasound is highly sensitive and specific for linear foreign bodies. Findings include a hyperechoic linear structure within the intestinal lumen, plication of the intestines (multiple loops of bowel gathered together), thickening of the intestinal wall, and reduced motility. Free abdominal fluid may be seen if peritonitis is present. CT: Computed tomography can provide detailed cross-sectional images and may be useful in complex cases, but is not routinely necessary. It can show the foreign body, plication, and complications such as perforation or abscess. Fluoroscopy: In some cases, fluoroscopy during contrast administration can help identify the foreign body and assess motility.

Cytology: If abdominal fluid is collected, cytology may reveal septic suppurative inflammation (degenerate neutrophils with intracellular bacteria) in cases of peritonitis. Histopathology: If intestinal resection is performed, histopathology of the affected segment may show transmural necrosis, ulceration, and inflammatory infiltrate. In chronic cases, fibrosis and granulomatous inflammation may be present. If a mass is found, histopathology can rule out neoplasia. In cases of intussusception, the resected segment may show ischemic necrosis of the invaginated portion.

Treatment of linear foreign bodies depends on the severity and duration of clinical signs. In early, uncomplicated cases where the foreign body is still in the stomach or proximal small intestine and the animal is stable, endoscopic retrieval may be attempted. However, if the foreign body has passed into the small intestine and plication is present, surgical intervention is usually required. Surgical options include: 1) Enterotomy: If the foreign body is accessible and the intestine is viable, a single or multiple enterotomies may be performed to remove the foreign body. The foreign body is carefully cut and removed in segments, ensuring that all pieces are retrieved. 2) Resection and anastomosis: If the intestine is non-viable (necrotic, perforated) or if multiple enterotomies would compromise the blood supply, the affected segment is resected and an end-to-end anastomosis is performed. 3) In cases where the foreign body is anchored at the pylorus or base of the tongue, it may be released via gastrotomy or oral extraction, respectively. Preoperative stabilization is crucial: intravenous fluids to correct dehydration and electrolyte imbalances, antiemetics (e.g., maropitant 1 mg/kg IV q24h), and broad-spectrum antibiotics (e.g., ampicillin 22 mg/kg IV q8h and enrofloxacin 5 mg/kg IV q24h, or cefazolin 22 mg/kg IV q8h) if peritonitis is suspected. Postoperative care includes continued fluid therapy, pain management (opioids such as buprenorphine 0.01-0.02 mg/kg IV q8-12h, or fentanyl CRI at 2-5 mcg/kg/h), and nutritional support (early enteral feeding via esophagostomy tube if needed). The animal should be monitored for signs of peritonitis, and antibiotics should be continued if infection was present.

The prognosis for linear foreign bodies is generally good if treated early and without complications. In uncomplicated cases where surgery is performed before perforation, the survival rate is high (over 90%). However, if peritonitis has developed, the prognosis is guarded, with mortality rates up to 50% in severe cases. Factors that worsen prognosis include delayed presentation, presence of perforation, septic peritonitis, and concurrent intussusception. Postoperative complications such as dehiscence, stricture, or adhesion formation can also affect outcome. With prompt surgical intervention and appropriate postoperative care, most animals recover fully and return to normal function.

Postoperative follow-up is essential to monitor recovery and detect complications. The animal should be re-examined within 10-14 days for suture removal (if skin sutures are present). Serial abdominal radiographs or ultrasound may be performed at 4, 8, and 12 weeks postoperatively to assess healing and ensure no recurrence or stricture formation. Activity should be restricted for 2-4 weeks to allow proper healing. A gradual return to normal diet is recommended, starting with small, frequent meals of a bland diet. Owners should be advised to monitor for signs of vomiting, diarrhea, or abdominal pain, which may indicate complications. Long-term follow-up may include regular veterinary check-ups and monitoring for any signs of intestinal dysfunction. In cases where a foreign body was removed, owners should be counseled on preventing future ingestion by removing access to linear objects and providing appropriate toys and environmental enrichment.

Pearls: 1) Always examine the oral cavity of cats with vomiting for a string under the tongue; if found, cut it and do not pull. 2) On abdominal palpation, plicated intestines feel like a 'bunch of grapes' or 'accordion'. 3) In surgery, carefully trace the entire length of the foreign body to ensure complete removal; multiple enterotomies may be needed. 4) If the intestine is severely compromised, do not hesitate to resect and anastomose. 5) Use a stay suture or Babcock forceps to handle the intestine gently. 6) Consider an esophagostomy tube for nutritional support in cases of prolonged anorexia. Pitfalls: 1) Pulling on the foreign body during surgery can cause further tearing of the intestine; always cut and remove in segments. 2) Missing a second foreign body or a piece of the original can lead to recurrence. 3) Inadequate preoperative stabilization can lead to intraoperative hypotension and complications. 4) Failure to recognize and treat peritonitis promptly can be fatal. 5) Using non-absorbable sutures in an infected field can lead to sinus tract formation; use monofilament absorbable sutures (e.g., polydioxanone) for intestinal closure.

Perioperative antimicrobial prophylaxis: Cefazolin 22 mg/kg IV at induction and repeated every 90 minutes during surgery. If peritonitis is present, continue antibiotics postoperatively: ampicillin 22 mg/kg IV q8h and enrofloxacin 5 mg/kg IV q24h, or a combination of clindamycin (11 mg/kg IV q12h) and a third-generation cephalosporin (e.g., cefovecin 8 mg/kg SC q14d). Analgesia: Preoperative: buprenorphine 0.01-0.02 mg/kg IV or IM. Intraoperative: fentanyl CRI at 5-10 mcg/kg/h. Postoperative: fentanyl CRI at 2-5 mcg/kg/h for 24-48 hours, then transition to oral opioids (tramadol 2-5 mg/kg PO q8-12h) or NSAIDs (carprofen 2.2 mg/kg PO q12h, or meloxicam 0.1 mg/kg PO q24h) if no contraindications. Antiemetics: Maropitant 1 mg/kg IV q24h or ondansetron 0.5-1 mg/kg IV q12h. Gastroprotectants: Omeprazole 1 mg/kg IV q24h or famotidine 0.5 mg/kg IV q12h. Fluid therapy: Balanced crystalloids (e.g., Lactated Ringer's solution) at a rate to correct dehydration (e.g., 60-100 ml/kg/day) and maintain perfusion. Potassium supplementation as needed. Nutritional support: If an esophagostomy tube is placed, a balanced liquid diet (e.g., Hill's a/d) can be started 12-24 hours postoperatively.

Several studies have evaluated the management and outcomes of linear foreign bodies in small animals. A retrospective study by Hayes (2009) in cats found that the most common linear foreign bodies were thread and string, and that surgical removal via enterotomy was required in 80% of cases. The study reported a survival rate of 95% when surgery was performed before perforation. Another study by Papazoglou et al. (2010) in dogs reported similar findings, with a higher incidence in young dogs and a good prognosis with early intervention. A study by Banzato et al. (2017) compared ultrasonographic findings with surgical findings and found that ultrasound had a sensitivity of 100% for detecting linear foreign bodies. Regarding surgical techniques, a study by Gagnon et al. (2014) compared single versus multiple enterotomies and found no significant difference in complication rates, but multiple enterotomies were associated with longer surgical time. A consensus statement from the American College of Veterinary Surgeons (ACVS) recommends early surgical intervention in cases of linear foreign bodies with plication, and emphasizes the importance of thorough exploration to ensure complete removal. Overall, the literature supports a favorable prognosis with prompt diagnosis and surgical management.