NAVLE Gastroenterology · ⏱ 10 min read · 📅 Mar 28, 2026 · by NAVLE Exam Prep Team · 👁 0

Bovine Abomasal Displacement (LDA and RDA): NAVLE Study Guide

Abomasal displacement is one of the highest-yield bovine GI topics on the NAVLE. The exam loves to give you a fresh dairy cow – high-producing Holstein, within 6 weeks of calving – with decreased milk, inappetence, and a ping. Your job is to know which side, what it means, and what to do about it.

Why It Happens

The abomasum sits on the right side of the abdominal floor in a normal cow. When motility drops, gas accumulates and the abomasum floats upward and migrates left (LDA, ~85% of cases) or stays right and balloons outward (RDA, ~15%). The key predisposing factor is decreased abomasal motility – and almost everything that stresses a fresh cow can cause it.

Risk factors cluster around the transition period. Negative energy balance from high-grain/low-fiber diets reduces rumen fill, giving the abomasum room to move. Concurrent diseases – metritis, mastitis, retained fetal membranes, and hypocalcemia – are the big four. Hypocalcemia directly impairs smooth muscle contractility throughout the GI tract. Retrospective studies show metritis or retained placenta co-occurs in roughly 38% of LDA cases. When the NAVLE gives you an LDA, always think: what else is wrong with this cow?

Classic NAVLE Trap The alkalosis paradox. Abomasal fluid is rich in HCl. When the abomasum is displaced and outflow is obstructed, that acid gets trapped – it never reaches the intestine to be absorbed. Chloride falls. Bicarbonate rises. The result is hypochloremic, hypokalemic metabolic alkalosis – NOT acidosis. Many students reflexively answer "metabolic acidosis" for any GI obstruction. For abomasal displacement, that is wrong. The kidneys try to conserve sodium by excreting H² and K², which is why you also get paradoxical aciduria despite systemic alkalosis.

LDA: Clinical Presentation and Diagnosis

The classic patient is a high-producing Holstein cow, within 4–6 weeks postpartum, showing decreased milk production, inappetence, mild ketosis, and reduced fecal output. She is not in shock. She is not collapsing. LDA is not an emergency – that distinction matters on the NAVLE.

Physical exam: reduced rumen fill on the left, medially displaced rumen on rectal, and the diagnostic finding – a high-pitched metallic ping on simultaneous auscultation and percussion of the left paralumbar fossa, 9th to 13th intercostal space. Ballottement over the same area produces a fluid splashing sound. The rumen ping is lower-pitched, more caudal, and in the left paralumbar fossa rather than the rib spaces – keep that distinction clear.

NAVLE Pearl Left-sided ping = LDA. Not an emergency. Right-sided ping = RDA. Watch closely for progression to abomasal volvulus – that IS an emergency. The ping location tells you everything about urgency.

RDA and Abomasal Volvulus

RDA presents similarly to LDA but on the right side. The ping sits in the right paralumbar fossa, roughly the 10th intercostal space to the paralumbar fossa. Clinical signs are generally more severe than LDA. The cow is sicker, more depressed, and you need to monitor her closely because RDA can progress to abomasal volvulus (AV).

Abomasal volvulus is when the abomasum twists, typically 270° counterclockwise, cutting off its own blood supply. This is a true emergency. The ping extends cranially to rib 8 (larger than in simple RDA), the liver displaces medially, and the cow is systemically ill – tachycardia >100 bpm, cold extremities, weak pulses, signs of shock. Serum lactate >4 mmol/L and elevated creatinine are poor prognostic indicators. These cows need emergency right flank laparotomy immediately.

Feature	LDA	RDA	Abomasal Volvulus (AV)
Frequency	~85% of cases	~15% of cases	RDA that has progressed
Ping location	Left, 9th–13th ICS	Right, 10th ICS → paralumbar fossa	Right, extends cranially to rib 8; large ping
Systemic illness	Mild; NOT emergency	Moderate; monitor closely	Severe; shock; EMERGENCY
Heart rate	Normal to mildly elevated	Mild–moderate tachycardia	≥100 bpm, often ≥120 bpm
Metabolic findings	Mild hypochloremic alkalosis	Moderate hypochloremic alkalosis	Severe alkalosis; elevated lactate and creatinine
Surgical approach	Right flank omentopexy (most common); roll & toggle	Right flank omentopexy	Emergency right flank laparotomy

Diagnosis: Lab Findings

The hallmark lab abnormality is hypochloremic, hypokalemic metabolic alkalosis. Serum chloride falls below normal (normal ~98–106 mEq/L). Bicarbonate rises. Potassium drops as the kidneys sacrifice K² and H² in exchange for sodium – paradoxical aciduria despite systemic alkalosis. In severe RDA or AV, expect elevated BUN and creatinine (prerenal azotemia from hypovolemia) and elevated lactate reflecting tissue hypoperfusion.

Abomasal outflow obstruction
HCl trapped

→

Cl² sequestered
HCO³ rises

→

Hypochloremic metabolic alkalosis
+ paradoxical aciduria

Treatment

Before surgery, address concurrent problems. Hypocalcemia is common – give IV calcium. Correct the alkalosis with IV NaCl (not lactated Ringer's). For the abomasum itself, three options exist for LDA:

Right flank laparotomy + omentopexy is the gold standard – standing surgery, done under local anesthesia on the right side, allowing direct visualization and permanent anchoring of the abomasum via omentum. Lowest recurrence rate, best long-term outcome.

Left paralumbar fossa laparotomy gives direct access to the displaced abomasum but is less commonly performed.

Roll and toggle (blind tack) is non-surgical and cheaper. The cow is cast and rolled into dorsal recumbency; the gas-filled abomasum floats back to the right. A toggle is placed percutaneously to anchor it. The downside: 50–60% recurrence rate with rolling alone (without toggle), and even with toggle there is risk of infection and misplacement. On the NAVLE, know that roll alone has a high recurrence – about 50–60%.

Postoperatively, erythromycin at 8.8–10 mg/kg IM acts as a motilin agonist to promote abomasal emptying and reduce hypomotility recurrence. It is the best-documented prokinetic for cattle post-LDA correction.

NAVLE Tip Treat the whole cow, not just the abomasum. Concurrent metritis, mastitis, or hypocalcemia drove the displacement in the first place. A cow that goes back to a herd with unresolved metritis and a diet unchanged from what caused the problem will likely displace again. Prevention means adequate dietary fiber (particle length ≥5 cm), avoiding overconditioned cows at calving (BCS >3.5 increases risk), and gradual concentrate introduction in transition.

NAVLE Exam Framing

The classic board question gives you a postpartum Holstein, 1–3 weeks fresh, with decreased milk and the key physical exam finding – a ping. They will test whether you know the ping is on the left for LDA (not emergency) versus right for RDA (watch for volvulus). They love to test the electrolyte abnormality – expect a serum chemistry showing low chloride and metabolic alkalosis, then ask you to explain why. The surgical correction question usually asks which technique offers the lowest recurrence (right flank omentopexy) or what the recurrence rate is for rolling alone (50–60%).

On the NAVLE, abomasal volvulus questions will give you a cow that had a mild right-sided ping a day or two ago, now presents collapsed and in shock. Elevated serum lactate above 4 mmol/L and elevated creatinine are the poor prognostic markers. Dark purple abomasal wall at surgery means ischemic necrosis – prognosis is guarded to poor regardless of how fast you operate.

Want full NAVLE study guides and timed practice questions?

Premium subscribers get condition-by-condition study guides, species-filtered practice questions, timed exam simulations, and a week-by-week study roadmap built for the boards.

Get Full Access — Start Free Trial →

Practice Questions

Test yourself before moving on. Click an answer to reveal the explanation.

Question 1 A 5-year-old Holstein dairy cow presents 10 days postpartum with decreased milk production, mild inappetence, and ketosis. On physical examination, simultaneous auscultation and percussion reveals a high-pitched metallic ping over the left paralumbar fossa between the 9th and 12th intercostal spaces. Rumen contractions are reduced. What is the most likely diagnosis?

Question 2 A 6-year-old Holstein cow, 8 days postpartum, presents with acute depression, right-sided abdominal distension, and a heart rate of 120 bpm. A high-pitched ping is heard from the 8th rib to the right paralumbar fossa. The cow has cold extremities and weak pulses. Serum chemistry reveals chloride 76 mEq/L, bicarbonate 36 mEq/L, potassium 2.3 mEq/L, and serum lactate 6.2 mmol/L. What is the most likely diagnosis and appropriate next step?

Question 3 A veterinarian confirms LDA in a 4-year-old dairy cow and performs right flank omentopexy. Preoperative bloodwork shows chloride 85 mEq/L, pH 7.53, base excess +14 mEq/L, and potassium 2.6 mEq/L. Which IV fluid is most appropriate for preoperative correction of the metabolic derangement?

Question 4 A farmer asks about correcting LDA in his cow using the roll-and-toggle technique without surgery. He wants to know the approximate recurrence rate if the cow is successfully rolled back into position but no toggle is placed. What is the most accurate estimate?

Question 5 A 5-year-old beef cow presents with fever (39.9 C), tachycardia (96 bpm), decreased appetite, and an arched back posture. She was treated with flunixin meglumine for 7 consecutive days for foot rot. Abdominocentesis yields cloudy fluid with total protein 4.8 g/dL and degenerate neutrophils. Fecal occult blood test is positive. There is no abomasal ping. Which of the following best explains the pathophysiology of this presentation?