Intra-abdominal infection (IAI, also spelled intraabdominal) is a group of

infections An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...

that occur within the

abdominal cavity The abdominal cavity is a large body cavity in humans and many other animals that contains many organs. It is a part of the abdominopelvic cavity. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is th ...

. They vary from

appendicitis Appendicitis is inflammation of the appendix. Symptoms commonly include right lower abdominal pain, nausea, vomiting, and decreased appetite. However, approximately 40% of people do not have these typical symptoms. Severe complications of a r ...

fecal peritonitis Peritonitis is inflammation of the localized or generalized peritoneum, the lining of the inner wall of the abdomen and cover of the abdominal organs. Symptoms may include severe pain, swelling of the abdomen, fever, or weight loss. One part ...

. Risk of death despite treatment is often high.

Classifications

IAIs can be classified into uncomplicated and complicated infections. Uncomplicated infections often involved the infection of single organ and can be controlled by surgical removal of the source of infection, and antibiotics is not required after the surgery to control the infection. In complicated infections, the infection spread to a part or to the whole of the

peritoneum The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mesot ...

, causing

peritonitis Peritonitis is inflammation of the localized or generalized peritoneum, the lining of the inner wall of the abdomen and cover of the abdominal organs. Symptoms may include severe pain, swelling of the abdomen, fever, or weight loss. One part or ...

. Meanwhile, peritonitis can be classified into primary, secondary, and tertiary peritonitis. Primary peritonitis is the diffuse bacterial infection of the peritoneum while the integrity of the gastrointestinal tract is preserved (in cases of

ascites Ascites is the abnormal build-up of fluid in the abdomen. Technically, it is more than 25 ml of fluid in the peritoneal cavity, although volumes greater than one liter may occur. Symptoms may include increased abdominal size, increased weight, a ...

); secondary peritonitis is the infection of peritoneum where the integrity of gastrointestinal tract is compromised; tertiary peritonitis is reinfection of peritoneum 48 hours after apparently good surgical control of secondary peritonitis.

Signs and symptoms

Those with suspected with IAIs usually have acute onset of abdominal pain with signs of local or generalised

inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...

s such as pain, tenderness (pain on touching), fever,

tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal ( ...

(increased heart rate), or

tachypnea Tachypnea, also spelt tachypnoea, is a respiratory rate greater than normal, resulting in abnormally rapid and shallow breathing. In adult humans at rest, any respiratory rate of 1220 per minute is considered clinically normal, with tachypnea be ...

(increased breathing rate). In more severe cases, such as organ failure, signs such as

hypotension Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure (the top number) and the dia ...

(low blood pressure),

oliguria Oliguria or hypouresis is the low output of urine specifically more than 80 ml/day but less than 400ml/day.Boon et al, Davidson's Principles & Practice of Medicine (20th Ed), p475 The decreased output of urine may be a sign of dehydration, kidney ...

(reduced urine output), sudden onset of

altered level of consciousness An altered level of consciousness is any measure of arousal other than normal. Level of consciousness (LOC) is a measurement of a person's arousability and responsiveness to stimuli from the environment. A mildly depressed level of consciousn ...

, and

lactic acidosis Lactic acidosis is a medical condition characterized by a build-up of lactate (especially -lactate) in the body, with formation of an excessively low pH in the bloodstream. It is a form of metabolic acidosis, in which excessive acid accumulates d ...

will appear. In case of

, signs such as fever, positive

psoas sign The psoas sign, also known as Cope's sign (or Cope's psoas test) or Obraztsova's sign, is a medical sign that indicates irritation to the iliopsoas group of hip flexors in the abdomen, and consequently indicates that the inflamed appendix is r ...

, migration of pain from umbilicus to the

right iliac fossa The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso ...

increases the likelihood of the disease; while signs such as vomiting before the pain reduces its likelihood to occur.

Diagnosis

CT scan and ultrasound has been used routinely to complete the assessment of IAIs. CT scan has higher sensitivity and specificity than ultrasound to access the condition. However, CT scan poses radiation risk to the subject. MRI scan is less readily available than CT scan or ultrasound in hospitals to diagnose IAIs. However, it has been proposed to be used in those who are pregnant and have inconclusive findings on ultrasound. The sensitivity and specificity of MRI in diagnosing acute appendicitis are 94% and 96% respectively. Laparoscopic surgery has also been used to diagnose the cause of IAIs when imaging is unhelpful. Besides, the laparoscopic surgery can also initiate treatment in the same setting. The accuracy is very high, in the range of 86 to 100%.

References

{{reflist General surgery