Perforation of the wall of the reticulum by a sharp foreign body produces initially an acute local peritonitis which may spread to cause acute diffuse peritonitis or remain localized to cause subsequent damage including vagal indigestion and diaphragmatic hernia. The penetration of the foreign body may proceed beyond the peritoneum and cause involvement of other organs resulting in pericarditis, cardiac tamponade, pneumonia, pleurisy and mediastinitis, and hepatic, splenic or diaphragmatic abscess.
Perforation of the wall of the reticulum by a sharp foreign body produces initially an acute local peritonitis characterized clinically by sudden anorexia and fall in milk yield, mild fever, ruminal stasis and local pain in the abdomen. Rapid recovery may occur, or the disease may persist in a chronic form or spread widely to produce an acute, diffuse peritonitis.
Most cases are caused by the ingestion of foreign bodies in prepared feed. Baling or fencing wire which has passed through a chaff-cutter, feed chopper or forage harvester is the commonest cause of injury. In one series of 1400 necropsies, 58 per cent of lesions were caused by wire, 36 per cent by nails and 6 per cent by miscellaneous objects. Adult dairy cattle are most commonly affected because of their more frequent exposure but cases occur infrequently in yearlings, beef cattle, dairy bulls, sheep and goats.
The disease is of great economic importance because of the severe loss of production it causes and the high mortality rate. Many cases go unrecognized and many more make spontaneous recoveries.
Lack of oral discrimination in cattle leads to the ingestion of foreign bodies which would be rejected by other species. Swallowed foreign bodies may lodge in the upper oesophagus and cause obstruction, or in the oesophageal groove and cause vomiting but in most instances they pass to the reticulum. Many lie there without causing harm but the cell-like structure of the lining provides many spots for fixation of the foreign body and the vigorous contractions of the reticulum are sufficient to push a sharppointed object through the wall. Most perforations occur in the lower part of the anterior wall but some occur laterally in the direction of the spleen and medially towards the liver.
If the wall is injured without penetration to the serous surface no detectable illness occurs, and the foreign body may remain fixed in the site for long periods and gradually be corroded away.
The initial reaction to perforation is one of acute local peritonitis, and in experimentally induced cases, clinical signs commence about 24 hours after penetration. The peritonitis causes ruminal atony and abdominal pain. If the foreign body falls back into the reticulum spontaneous recovery may occur, although spread of the inflammation to affect most of the peritoneal cavity is likely to occur in cows which calve at the time of perforation, and in cattle which are forced to exercise. Immobility is a prominent sign of the disease and it serves as a protective mechanism in that adhesions are able to form and localize the peritonitis. Animals made to walk or transported long distances frequently suffer relapses when these adhesions are broken down during body movements.
During the initial penetration the foreign body may penetrate beyond the peritoneal cavity and into the pleural or pericardial sacs to set up inflammation there. It is often stated that foreign bodies which remain embedded in the reticular wall may be pushed further by the pressure of the calf during late pregnancy or the efforts of parturition. At least it can be said that signs are more likely to occur in cows after the sixth month of pregnancy.
The pathogenesis of the more common complications are discussed under traumatic pericarditis, vagus indigestion, diaphragmatic hernia and traumatic abscess of the spleen and liver. Less common sequelae include rupture of the left gastro-epiploic artery causing sudden death due to internal hemorrhage and the development of a diaphragmatic abscess which infiltrates tissues to the ventral abdominal wall at the xiphoid process, rupturing to the exterior and sometimes discharging the foreign body. Hematogenous spread of infection from a diaphragmatic abscess or chronic local peritonitis is one of the commonest causes of endocarditis and its attendant lesions of arthritis, nephritis and pulmonary abscess. Penetration into the pleural cavity causes development of an acute suppurative pleurisy and pneumonia. In rare cases the infection is localized chiefly to the mediastinum with the development of an extensive abscess which causes pressure on the pericardial sac and resulting cardiac embarrassment and congestive heart failure.
The onset is sudden with complete anorexia and a sharp fall in milk yield usually to about a third of the previous yield. These changes occur within a 12 hour period and their abrupt appearance is typical of this disease. There is subacute abdominal pain in all cases. The animal is reluctant to move and does so slowly. Walking, particularly downhill, is often accompanied by grunting. Most animals prefer to remain standing for long periods and lie down with great care; habitual recumbency is characteristic in others. Arching of the back is marked in about half of the cases but there is always rigidity of the back and of the abdominal muscles so that the animal appears gaunt or tucked-up. Defecation and urination cause pain and the acts are performed infrequently and usually with grunting. In rare cases an attack of acute abdominal pain with kicking at the belly, stretching and rolling is the earliest sign. In others there is recumbency and inability to rise.
A moderate systemic reaction occurs, the temperature rising usually to 39.5 to 40Qc (103 to 1040F), rarely higher, pulse rate to about 80 per minute and the respiratory rate to about 30 per minute. The respirations are usually shallow and, if the pleural cavity has been penetrated, are painful and accompanied by an audible expiratory grunt. Rumination is suspended and ruminal movements are absent, or at least severely depressed to a rate of about 1 per 2 minutes with the sounds much reduced in intensity. The rumen may appear to be full because of the presence of mild tympany and in some cases there is moderate distension of the left flank. On palpation a typical cap of gas can be felt before the firm doughy ruminal contents are reached. The presence of this cap is caused by the separation of the gas from the sold and fluid contents and may occur in other forms of acute ruminal atony. Constipation is always present.
Pain can be elicited by vigorous palpation of the abdominal wall just behind the xiphoid process of the sternum. Pressure can be exerted by a short, sharp jab with the closed fist or knee. Pinching the withers to cause depression of the back or sharp elevation of a rail held under the abdomen are much less satisfactory.
The development of acute diffuse peritonitis is manifested by the appearance of a profound toxaemia within a day or two of the onset of local peritonitis. Alimentary tract movements cease entirely, there is severe depression and the temperature may be higher than normal, or subnormal in fulminating cases, especially those which occur immediately after calving. The pulse rate rises to 100 to 120 per minute and pain can be elicited by palpation anywhere over the ventral abdominal wall.
The diseases which are commonly confused with traumatic reticuloperitonitis are ketosis, indigestion, rumen overload, abomasal displacement or torsion, impaction of the omasum, pyelonephritis and hepatic abscess or fascioliasis. Acute local peritonitis can be differentiated from indigestion, acute ruminal impaction and acetonaemia by the presence of fever, local abdominal pain and the abrupt fall in milk yield and appetite. Pyelonephritis can be distinguished by the presence of pus and blood in the urine and abomasal displacement by the presence of abomasal sounds in the left flank. Acute ruminal impaction is a much more serious disease and is usually accompanied by a marked increase in heart rate, staggering, recumbency, blindness and hypothermia.
Traumatic reticuloperitonitis usually causes a secondary acetonaemia when it occurs during early lactation and the presence of ketonuria should not be used as the sole basis for differentiation of the disease.
Two methods of treatment are in general use, conservative treatment with or without the use of a magnet, and rumenotomy.
Conservative treatment comprises immobilization of the animal, administration of antibacterial drugs to control infection and possibly the oral administration of a magnet to immobilize the foreign body. The cow is tied or stanchioned and not moved for 10 to 14 days. Milking, feeding and watering are carried out on the spot. The immobilization facilitates the formation of adhesions and this, and removal of the foreign body, may be further aided by standing the animal on an inclined plane made of a door or planks or by packing earth under the front feet of the cow.
Antibacterial treatment may be provided by the oral administration of sulphonamide (l g. per lb. body weight daily for 3 to 5 days) or parenteral injections of antibiotics, usually a combination of penicillin and streptomycin, for 3 days.
Small cylindrical or bar magnets, 7.5 cm. long by 1.0 to 2.5 cm. diameter with rounded ends have been developed as prophylactic measure against traumatic reticuloperitonitis but they have also come into fairly general use as an aid to treatment. It is unlikely that they will extract a firmly embedded foreign body from the wall of the reticulum but loosely embedded ones with long free ends may be returned to the reticulum and loose foreign bodies will be immobilized. Used prophylactically they reduce the incidence of the disease a great deal provided they lodge in the reticulum. However, many pass straight through into the rumen unless the amount of roughage fed is reduced for 24 hours beforehand.
Surgical removal of the foreign body through a rumenotomy incision is widely used as a primary treatment. It has the advantage of being both a satisfactory treatment and diagnostic procedure.