Introduction

Trauma to the abdomen and resulting injury to the intraabdominal viscera is frequently seen in veterinary practice and accounts for significant morbidity and mortality rates. This is understandable because the abdominal organs are quite vulnerable since most of these are not protected by a bone case. Causes of injury may be penetrating trauma with perforation and laceration of body wall and abdominal viscera or blunt trauma with contusion, laceration, avulsion or rupture of abdominal organs. The common blunt compression trauma may induce massive organ shattering and fatal haemorrhage of liver and spleen, and is certainly not less serious than the more obvious penetrating trauma with consequent damage to the intestines or liver.

There are four important consequences of abdominal trauma: haemorrhage--peritonitis--uraemia--organ function impairment. Abdominal haemorrhage is most apparent with injuries to the liver, spleen and kidneys, and with injuries to major vessels as caudal vena cava, splenic or renal arteries, portal vein and mesenteric vessels. Peritonitis (chemical or septic) develops as a result of rupture of a hollow viscus or trauma to the pancreas. Uraemia is caused by leakage of larger quantities of urine into the (retro-)peritoneal space as a result of bilateral renal or ureteral injuries or rupture of the urinary bladder or urethra. Organ function impairment depends upon the type, location, duration and degree of organ disruption from injury.

Radiography

Abdominal survey radiography and contrast studies are very useful for diagnosing the severity of abdominal trauma and are helpful in reaching a conclusion of whether or not surgical intervention is indicated. As an example, the presence of free gas in the peritoneal space is an indication for acute celiotomy.

As a rule for contrast examinations, intravenous iodine-studies should be given priority over barium studies since they do not interfere with visibility of intra-abdominal viscera and details, and are less irritative when accidentally leaked into the peritoneal cavity due to gastrointestinal perforation. Evaluation of abdominal radiographs of the traumatized animal must be performed carefully and systematically. The peripheral soft tissues, surrounding bony structures, peritoneal cavity, abdominal viscera and retroperitoneal space are scrutinized.

Peripheral soft tissue trauma includes herniae with displacement of viscera outside the abdominal cavity through diaphragmatic, inguinal, perineal, ventral, or umbilical tear or rupture. Soft tissue swelling as haematoma's may indicate possible damage to underlying viscera. Fractures of surrounding bony structures may indicate trauma to adjacent viscera as seen in cases of rupture of the urinary bladder or urethra due to pelvic fractures. Positive iodine-contrast retrograde urethro-cystography may be necessary to positively identify these lesions. In evaluating the (retro)peritoneal and abdominal viscera an effort should be made to identify as many structures as possible.

Radiographic signs of intra-abdominal trauma include the following:

1.  generalized, increased density due to free peritoneal fluid

a.  haemoperitoneum, hydroperitoneum

b.  passive congestive peritoneum

c.  peritonitis

2.  localized, ill-defined density

a.  localized haemorrhage

b.  localized peritonitis, rupture

3.  organ enlargement due to subcapsular or intraparenchymal haemorrhage

4.  free peritoneal gas due to perforation or rupture of a hollow viscus or body wall

5.  herniations: diaphragmatic, paracostal, umbilical, ventral, inguinal, etc.

Loss of abdominal structures and serosal margins on radiographs of a mature well-fed animal indicate the presence of free peritoneal fluid. The type of fluid cannot be distinguished radiographically. For this, paracentesis is necessary. Fluid accumulation may be indicative of haemoperitoneum due to rupture of the liver, spleen, or an abdominal vessel, or may indicate hydroperitoneum as a result of rupture of the urinary bladder, urethra, or gall-bladder. Contrast studies will confirm the presence of these suspected lesions. Also, peritonitis and passive congestion that are the result of volvulus, torsion, or incarcerated herniation may result in peritoneal fluid collection.

Free ingesta may be found following intestinal rupture .Local areas of poor serosal detail should be correlated with either localized haemorrhage of abdominal structures, or with localized peritonitis as seen with acute traumatic pancreatitis or intestinal perforation.

Organ enlargement may result from encapsulated haemorrhage, or passive congestion due to vascular compromise. Free peritoneal gas indicates the presence of a perforating wound or the possibility of gastrointestinal rupture. In this respect, it should be remembered that trapped air following abdominal surgery or pneumoperitoneography will be radiographically visible for several days or weeks. Normally, free peritoneal gas can be detected easily on routine non-contrast lateral and dorsoventral abdominal radiographs. Due to the presence of larger amounts of free gas the outlines of larger abdominal structures as spleen, liver, and kidneys is accentuated and the serosal surface of intestinal loops unusually sharply defined.

The detection of smaller amounts of free gas is more difficult. When only a small amount of gas is present the animal under investigation should be kept in position for several minutes to allow the gas to accumulate at the highest point of the peritoneal cavity before the radiographs are taken. In left-lateral recumbent position, gas will collect and will be visible as a radiolucent separation between the right diaphragmatic crusand the right liver shadow. In dorsoventral position, gas will accumulate around the kidneys. Only seldomly, horizontal-beam projections are necessary to localize and detect free intraperitoneal gas.

Trauma to the retroperitoneal space

Traumatic fluid collections of blood or urine in the retroperitoneal space will result in haziness of the caudodorsal abdominal area, with loss of the renal margins and with ventral displacement of the descending colon and rectum.

Radiographic signs of retroperitoneal trauma

 increased density of retroperitoneal space

 displacement, asymmetry or non

 visualization of kidneys

 ventral displacement of descending colon and rectum

 non-visualization of urinary bladder

 fractures of pelvis or vertebrae

Excretory urography will confirm traumatic lesions of the kidneys and ureters. In this respect, it is interesting to know that in traumatology of human medicine a system of interval radiography is used during the acute phase (first 6 hours) following blunt abdominal trauma. Films of the entire abdomen are made at 15 minutes interval during the first 1 hour, in combination with infusion excretory urography, in order to evaluate intra-abdominal changes that develop in time and that can be related to traumato the liver, spleen or urinary system. Based on these findings, a prognosis for surgical intervention or conservative therapy is presented.

Urinary tract trauma

Also in small animals, traumatic lesions of the urinary tract are frequently encountered. The urinary tract may be injured by external trauma such as perforating bite-wounds, fractures or even gun-shots, or by blunt trauma. In addition, it may also be injured by iatrogenic trauma such as urethral or bladderwall perforations, ureteral ligation or complications following surgery, e.g., strictures and adhesive obstructions. Radiographic techniques that can be used for evaluation of these injuries include:

 non-contrast abdominal radiography

 positive-contrast retrograde urethro-cystography

 excretory urography

 non-selective angiography

In animals with peritoneal ascites (hydroperitoneum) due to extravasation of urine, radiographic examination should be performed in the following order:

1.  non-contrast radiography of the abdomen

2.  positive-contrast retrograde urethro-cystography

3.  excretory urography

Radiographic signs of urinary tract trauma: non-contrast radiography

 displacement, asymmetry, or non-visualization of kidneys

 increased density in retroperitoneal space

 generalized increased density in peritoneal space

 non-visualization of urinary bladder

 over-distension of urinary bladder

 herniation of urinary bladder

 fractures of vertebrae or pelvis

 paralytic ileus

Radiographic signs of urinary tract trauma: positive-contrast retrograde urethro-cystography

 extravasation of contrast medium into the retroperitoneal space, peritoneal cavity, or wall of urinary bladder

 irregularities of internal outline of urinary bladder

 intraluminal blood cloths in urinary bladder

 urinary bladder displacement

 obstruction of urethral lumen

Radiographic signs of urinary tract trauma: excretory urography

 extravasation of contrast medium into renal subcapsular space, retroperitoneal space or peritoneal cavity

 renal tear or laceration

 ureteral rupture

 failure of opacification and/or excretion of one or both kidneys

 disruption of trenal vascular pedicle

 renal artery thrombosis

 ligation of ureter(s)

 hydroureter and hydronephrosis

 decreased ureteral peristalsis

 ureteral obstruction

As a last remark concerning abdominal trauma the following notes are very important. In small animals that fail to recover in the expected way following trauma, radiographic examination of the thorax and abdomen must be repeated, even when the initial radiographic examination revealed no abnormalities! It should always be remembered that abdominal haemorrhage may become visible only hours after the original traumatic incident, and that traumatic peritonitis or retroperitoneal accumulation of fluid may only become visible after days. And as an extra complication, traumatic shock lungs (ARDS) may develop after 24 hours and will certainly result in unexpected death when no proper therapy is installed.

Conclusion

Radiography is a very reliable, non-invasive method of establishing the presence, nature, site and extent of traumatic injuries to the thorax and abdomen of animals. It is confirmative and supplemental to the clinical examination. Besides that, radiographs form a permanent record that may be used as a basis for control of recovery and for evaluation of secondary acute respiratory distress syndrome.