Gastric dilatation-volvulus stabilization, surgery and prognosis in dogs

Doses on this pageEvery dose below is quoted from the cited source. Verify against the current label/formulary and the patient's full clinical picture.

Pathophysiology and who is affected

According to Merck, the stomach fills with gas and fluid and rotates around its axis. Whether dilation or rotation comes first is unsettled, although rotation first is the favored hypothesis [1]. Seen from caudal to cranial, the rotation is clockwise and ranges from 90 to 360 degrees. This moves the pylorus to the left of midline and traps the duodenum, and Merck states that rotation beyond 180 degrees closes off the distal esophagus [1]. The spleen is often displaced or trapped with the stomach [1].

The swollen stomach presses on the caudal vena cava and portal veins and reduces venous return. Merck describes the downstream effects as portal hypertension, gastrointestinal ischemia, hypovolemia and systemic hypotension. It adds that affected dogs are at risk of endotoxemia, hypoxemia, metabolic acidosis and disseminated intravascular coagulation [1].

Beyond breed and conformation, Merck lists these associated factors and reports no sex predisposition [1]:

• rising age
• lean body condition
• stress
• fearful or aggressive temperament
• feeding once a day
• feeding only dry kibble
• fast eating
• prior splenectomy
• lax gastric ligaments

A single-hospital retrospective study in Turin, Italy, covered 130 surgically treated dogs. German Shepherds made up 25.38% of cases, intact males 53.1%, and dogs aged 5 to 10 years 54.69% [4]. The authors noted that their findings were drawn from one facility and may reflect regional breed distribution [4].

Presentation and diagnosis

Merck describes nonproductive retching, drooling and restlessness, with a distended or tympanic abdomen; some dogs are found recumbent and depressed [1]. Shock signs include weak pulses, tachycardia, prolonged capillary refill and pale membranes [1]. An irregular rhythm with pulse deficits points to arrhythmia, and the enlarged stomach can restrict diaphragm movement and cause respiratory distress [1].

Radiographs separate simple dilation from GDV. Merck recommends right lateral and dorsoventral views [1]. On the right lateral view the pylorus sits dorsal and slightly cranial to the fundus. A soft tissue fold between them produces the compartmented "double bubble" sign [1]. Merck notes that gas in the gastric wall suggests compromised tissue and free abdominal gas indicates rupture [1].

For bloodwork, Merck lists a CBC, chemistry panel and coagulation tests, with particular attention to PCV, total solids, electrolytes, glucose and lactate [1]. Reported changes include prerenal azotemia, which Merck describes as common. Possible increases in CK, potassium and liver enzymes (the last from hypoxic injury) may also occur [1]. Merck states that lactate above 6 mmol/L is "associated with an increased likelihood of gastric necrosis and the need for partial gastric resection" [1]. Merck also recommends continuous ECG and blood pressure monitoring [1].

The cited sources do not describe a formal staging or grading system for GDV.

Stabilization before surgery

Merck sets two immediate goals, restoring circulating volume and decompressing the stomach, carried out at the same time [1].

Fluids. Merck advises one or more large-bore catheters in cranial veins such as the jugular or cephalic. It recommends avoiding hindlimb veins because the distended stomach can impair return from the hind end [1]. It describes crystalloids at a shock rate of "90 mL/kg/hour" as the usual first choice [1]. It mentions colloids and hypertonic saline as alternatives, while cautioning that synthetic colloids carry kidney injury and coagulopathy risk [1]. Merck notes that fluid rates "are guidelines only" and must be tailored to the patient [1].

Supportive care. Merck lists flow-by oxygen. It notes that antimicrobials such as ampicillin are often given because of endotoxemia and bacterial translocation risk [1]. Electrolyte and acid-base problems usually resolve with fluids and decompression, according to Merck [1].

Decompression. Merck describes orogastric intubation and percutaneous trocarization as both effective, with the choice depending on experience and equipment [1].

• Tube placement. Merck mentions sedation with fentanyl or hydromorphone, with or without diazepam, and advises avoiding vasodilating drugs such as phenothiazines [1]. The tube is premeasured from the incisors to the last rib and should not pass that mark. Merck warns that esophageal or gastric perforation is possible [1]. After decompression, Merck describes lavage with warm water to slow redilation [1].
• Trocarization. Merck describes a clipped, prepared site on the right body wall behind the last rib. The site is chosen by percussing for tympany to avoid puncturing the spleen, with the left paracostal area as the fallback [1].

Surgery and postoperative care

Merck describes a cranioventral midline approach and decompression before the stomach is repositioned. The stomach and spleen are then assessed for ischemia and thrombosis [1]. Ischemic gastric wall is removed and splenectomy performed if needed. Merck calls extensive gastric necrosis and necrosis of the cardia poor prognostic signs [1]. A gastropexy follows, with incisional and belt-loop techniques named by Merck as the most common [1].

In the Turin cohort, the hospital moved from belt-loop to incisional gastropexy and stopped using belt-loop by 2021. The authors found no significant difference between the techniques for survival or postoperative complications [4]. Overall complications occurred in 66 of 130 dogs (50.8%) [4].

After surgery, Merck lists IV fluids, analgesia and withholding food for 12 to 48 hours. Antiemetics such as metoclopramide or maropitant may be given if vomiting continues [1]. Merck states that postoperative arrhythmias are common but often need no treatment, and gives these triggers for antiarrhythmic therapy [1]:

• persistent tachycardia above 140 bpm
• systolic pressure below 90 mm Hg
• hypoperfusion such as prolonged capillary refill or weak pulses
• an "R on T" pattern
• multifocal ventricular premature contractions

Merck names lidocaine as the first-line drug, procainamide for poor response, and magnesium sulfate for life-threatening arrhythmias [1]. In the Turin cohort, lidocaine infusions were used in 53% of the 90 dogs with postoperative records [4].

Lactate and prognosis

Merck gives differing mortality figures: 20% in treated animals in its opening, 20-45% in its key points, and an overall figure of about 25-30% [1]. The Turin study reported survival of 86.4% (102 of 118 dogs with outcome data) [4]. That figure comes from one retrospective cohort that excluded 43 dogs whose owners declined surgery. The authors noted the cohort includes only dogs that reached the operating room [4].

The Veterinary Evidence summary by David Mackenzie appraised 15 studies, 12 retrospective and 3 prospective [2]. Eleven found a significant difference in admission lactate between survivors and non-survivors and four did not [2]. Optimal cut-offs from ROC analysis ranged from 4.1 to 9.0 mmol/L. Sensitivity was moderately low and specificity higher [2]. The author concluded that a low lactate predicts survival better than a high lactate predicts death [2].

Two individual studies illustrate the range:

• De Papp et al. (1999). In this retrospective study of 102 dogs, 69 of 70 dogs with lactate below 6.0 mmol/L survived, compared with 18 of 31 above it. The review noted that 23 dogs received fluids before lactate was measured and were analysed together with untreated dogs [2].
• Zacher et al. (2010). In this retrospective study of 64 dogs, a fall in lactate of at least 42.2% after resuscitation predicted survival with 61% sensitivity and 100% specificity. The review flagged the small sample and the inclusion of dogs euthanised on a subjective impression of necrosis [2].

The summary's author wrote that lactate "should not be used to give a prognosis for individual patients" [2]. The author also wrote that exploratory laparotomy should be advised "irrespective of the blood lactate level" [2]. The Turin study found no significant link between lactate and mortality. However, lactate was recorded for only 34 of 130 dogs, which the authors said limited statistical power [4]. That study also found no significant association between splenectomy and death (p = 0.074), a result the authors attributed partly to the small number of deaths [4].

Recurrence after gastropexy

The second Veterinary Evidence summary, by Daniel Low, appraised 16 studies, including two prospective trials and eleven case series [3]. Recurrence after gastropexy ranged from 0% to 15.4% [3]. Gastrocolopexy attaches the stomach to the colon rather than the body wall. It had a 20% recurrence rate in one randomised trial, and the author said it should not be treated as equivalent [3]. The author judged the overall evidence weak and likely to underestimate true recurrence, because follow-up was short and often relied on owner or referring-vet reports [3].

Control groups without gastropexy fared worse:

• Eggertsdottir et al. (1996). In this prospective trial of 31 dogs with unbalanced allocation, recurrence was 0 of 10 dogs with gastropexy, as reported by the review, and 3 of 8 without [3].
• Glickman et al. (1998). In this prospective multi-centre cohort, median survival was 547 days with gastropexy versus 188 days without [3].

In the Turin cohort, one dog died of recurrence more than six months after a belt-loop gastropexy [4]. Merck notes that gastropexy has not been shown to prevent dilation, only the volvulus [1].

Before using any dose aboveVerify against the current label/formulary and the patient's full clinical picture.