Traumatic reticuloperitonitis

What it is

Traumatic reticuloperitonitis (TRP), known as "hardware disease" or foreign body disease, occurs when a sharp ingested object, mainly nails and pieces of wire, perforates the wall of the reticulum. Cattle do not sort their feed with their lips and swallow without thorough chewing, so metallic objects reach the reticulum, the most cranial and ventral compartment, where they collect because of their weight. The strong contractions of the reticulum drive them into its wall, almost always in a cranioventral direction.

Perforation causes local peritonitis, which is usually walled off by fibrinous adhesions between the reticulum, diaphragm and abdominal wall, or diffuse peritonitis if it is not contained. The object can keep advancing and form abscesses in the liver or spleen, cross the diaphragm and cause pleuritis, or enter the pericardial sac and produce septic traumatic pericarditis, with fibrinopurulent exudate that compresses the heart and prevents its filling. Adhesions and abscesses can damage the vagus nerve and cause vagal indigestion.

Who it affects

Mainly adult cows, particularly dairy cows fed chopped forage or mixed rations, in which wire debris (from fences or from tyres used to cover silage) is shredded and mixed into the feed. Late pregnancy and calving, through increased abdominal pressure, favour perforation. It is uncommon in calves and in animals grazing pastures free of metal debris.

Anatomy involved

• Reticulum: lies against the abdominal surface of the diaphragm, opposite ribs 6 to 8. Its honeycomb mucosa traps heavy objects, and its biphasic contractions push them against the cranioventral wall, where most perforations occur.
• Diaphragm: the only thing separating the reticulum from the thoracic cavity. A foreign body that crosses it reaches the pleural space and the pericardium; adhesions can fix the reticulum to the diaphragm.
• Heart and pericardium: the heart lies a few centimetres from the reticulum, on the other side of the diaphragm. In traumatic pericarditis the pericardial sac fills with fluid and fibrin, and compression of the heart produces right-sided heart failure (venous congestion and oedema).
• Neighbouring organs: the liver, on the right, and the spleen, on the left, can develop abscesses; the vagus nerve can be involved in the adhesions.

Clinical signs

In the acute form there is a sudden onset of anorexia, drop in milk yield, fever, ruminal hypomotility or atony, sometimes mild bloat, an arched back, reluctance to move, a tense abdomen and grunting, spontaneously or on movement. Foreign body pain tests (pinching the withers, pressing a bar against the xiphoid region or percussing the cranioventral abdominal wall) aim to elicit that grunt. In the chronic form the signs are vague: erratic appetite, weight loss, low yield and poorly digested faeces.

In traumatic pericarditis there is tachycardia, muffled heart sounds, splashing or friction pericardial sounds, jugular vein distension and submandibular, brisket and ventral abdominal oedema.

Diagnosis

• Clinical examination: pain tests and general signs are suggestive but not conclusive. The main differential diagnosis is abomasal ulceration.
• Laboratory: markers of inflammation such as increased fibrinogen and total protein, leucocytosis and a shortened coagulation time in the glutaraldehyde test. Pericarditis also raises liver enzymes because of hepatic congestion.
• Ultrasonography of the reticulum through the ventral thoracic wall: shows fibrin deposits, adhesions, abscesses and reduced amplitude and frequency of reticular contractions.
• Radiography of the reticulum in the standing animal: the technique of choice to see metallic foreign bodies, their position and whether they are attached to a magnet.
• Pericarditis: ultrasonography is the method of choice to see pericardial effusion, fibrin on the epicardium and compression of the ventricles.

Treatment and prevention

• Conservative treatment: oral administration of a magnet, which lodges in the reticulum and holds the object, together with antimicrobials, anti-inflammatory drugs and, if needed, fluid therapy; rest in a confined space. The animal is re-evaluated, ideally radiographically, if it does not improve within a few days.
• Surgical treatment: left flank rumenotomy to remove the foreign body from inside the reticulum and drain accessible abscesses. It is reserved for cases in which the object does not attach to the magnet or there is no response to medical treatment.
• Traumatic pericarditis: the prognosis is very poor; pericardiocentesis and pericardiotomy rarely resolve it, so euthanasia or slaughter is indicated in most cases.
• Prevention: magnets on forage harvesters and feed mixer wagons, avoiding wire and worn tyres near the feed, and prophylactic magnets given to heifers before they join the adult herd.
• Drug use in food animals is subject to each country's regulations and to withdrawal periods for milk and meat.

Key studies

The available evidence comes mainly from one large retrospective series from a single hospital (Clinic of Ruminants, University of Zurich); there are no controlled treatment trials.

• Braun et al. (2018, clinical findings), retrospective study of 503 cattle with TRP. The most common findings were abnormal demeanour and general condition (87%), decreased rumen motility (72%), poorly digested faeces (57%), fever (43%) and tachycardia (26%). At least one of the three foreign body tests was positive in 58%, and all three were negative in 42%. Fibrinogen was increased in 69% and total protein in 64%; the glutaraldehyde test coagulated within 6 minutes in 75%. No single finding is enough for the diagnosis.
• Braun et al. (2018, imaging), same series: ultrasonography showed changes consistent with peritonitis in 83% and reduced or absent reticular motility in 37%. Radiographs showed foreign bodies in 96% and a magnet in 64%; of the foreign bodies not attached to a magnet, 12% had perforated the reticulum.
• Braun et al. (2018, treatment), same series: 232 animals were treated conservatively, 206 underwent surgery and 61 were slaughtered or euthanased. 90% of the operated and 82% of the medically treated cattle were discharged. Treatment was assigned by radiographic findings rather than at random, so the comparison between groups is biased; the authors recommend starting with a magnet and antibiotics and reserving surgery for when the object does not attach to the magnet.
• Braun et al. (2020), comparison of 503 cows with TRP, cows with type 1 to 5 abomasal ulcers and 182 healthy cows. Many signs, such as mild fever, scleral vessel congestion and positive foreign body tests, also occurred in healthy cows, and no single sign distinguished TRP from abomasal ulcer. Although the pain tests are taught as the key to diagnosis, on their own they are not reliable.
• Braun (2009), narrative review of traumatic pericarditis; it is the standard reference and there are no higher-level studies. It summarises that the glutaraldehyde test is positive in more than 90% of affected cattle, that ultrasonography is the method of choice for pericardial effusion and that the prognosis is poor, with euthanasia indicated.