An Overview of Abdominal Pain

We can hardly find a person who has not suffered from abdominal pain at least once in his life. Abdominal pain may be of different types, caused by a number of causes, which range from simple to life threatening conditions. Irrespective of the cause and the severity, it is troublesome for the sufferers and the caregivers, and hence forces them to go for a medical consultation.

Abdomen is the part of the body between the thorax and the pelvis, which is separated from the thorax by a diaphragm and from the true pelvis by an imaginary plane. Anteriorly the anterior abdominal wall supports it and posteriorly, the spine and back muscles. Skin, superficial fascia, deep fascia, muscles, layers of fascia (fascia transversalis), extra peritoneal connective tissue and the outer layer of peritoneum form the anterior abdominal wall. The abdominal cavity extends upwards in to the concavity of diaphragm and downwards in to the pelvic cavity. Since there is overlapping by the ribs in the upper part and pelvic bones in the lower part, the exact size of the abdominal cavity is masked.

The abdomen contains digestive organisms like stomach, small intestine, large intestine, liver, gall bladder, pancreas, and uro-genital veins like kidneys, ureters, bladder, fallopian tubes, ovaries and uterus. It also contains organs like spleen, adrenal glands, mesenteric lymph nodes, blood vessels and lymphatic vessels etc. Ligaments formed by peritoneal tissue attach these organs and keep them in position. The peritoneum is a large serous membrane lining the abdominal cavity and has got two layers. The outer layer is called parietal peritoneum and it covers the inner surface of the abdominal wall and the inner layer is called visceral peritoneum, which covers the organs and restricts their mobility. These two layers of peritoneum are connected by omentum and mesentery through which the organs get blood supply and nerve supply. The cavity formed by the two layers of peritoneum is a potential space, called peritoneal cavity, which is moistened by a serous fluid to avoid friction of abdominal contents.

Types of abdominal pain:

Depending upon the origin, there can be different types of abdominal pains.

1. Visceral pain (Splanchnic pain): This is caused by stimulation of visceral nerves by a noxious agent, which may be living organisms, toxins, mechanical stimuli like stretching, excess muscular contraction or an ischaemia. Visceral pain is dull in nature and is poorly localized and felt in the midline.

2. Parietal pain: This is also called somatic pain. Here, some noxious agents stimulate the parietal peritoneum causing a sharp and localized pain. This type of pain is worse by movements.

3. Referred pain: Here the pain, although originating in other sites, is felt in the abdomen due to common nerve supply. Example: Conditions like pleurisy, pericarditis, torsion of testes etc. cause pain in abdominal region due to supply of nerves having the same root value (Spinal segments).

It has already been mentioned that abdominal pain is agonizing for the affected person and his family members irrespective of its cause and severity. Intensity of pain may not always indicate the seriousness of the condition because severe pain can be from mild conditions like indigestion and flatulency, where as mild pain may be present in life threatening conditions like perforation, cancer etc. Here proper diagnosis and management is very essential.

Modes of presentation of abdominal pain:

1. Acute abdominal pain: Here, the pain is sudden with a rapid onset and short course, which may be due to severe or mild lesions. The term 'acute abdomen' is used in conditions wherein the patient complains of acute abdominal symptoms that suggest a disease, which definitely or possibly threatens life and may or may not demand urgent surgical interference. Acute pain may be colicky or non colicky in nature.

2. Chronic abdominal pain: Here the pain is long lasting and recurrent or characterized by long suffering. The complaints persist for a long time with fluctuations in the intensity of symptoms.

3. Sub acute abdominal pain: As the name indicates the duration of pain lies between acute and chronic conditions.

4. Acute exacerbation: In this state, a person having chronic symptoms comes with a sudden sunset of symptoms that simulate an acute condition. In such cases the patient or the bystanders give the history of chronic sufferings.

Causes of abdominal pain:

The etiology of abdominal pain can be discussed under the following headings.

A. Pain due to lesions in the abdomen: Example: Gastritis, Duodenitis, Appendicitis, Peritonitis, Pancreatitis, Intestinal obstruction, Renal colic, Cholecystitis, Gall stones with obstruction, Peptic ulcer, Intestinal perforation, Non ulcer dyspepsia, Liver abscess, Mesenteric lymphadenitis, Inflammatory bowel diseases (Ulcerative colitis, Crohn's disease), Dysentery, Cancer of the gastrointestinal tract (GIT), Abdominal TB, Abdominal migraine, Acute regional ileitis, etc.

B. Pain due to metabolic and general problems: Example: Poisoning, Renal failure, Diabetes, Thyroid problems, Hyper parathyroidism, Porphyria, Drugs, Lead colic, Black widow spider bite, Blood diseases, Malaria, Leukemia, Peri arteritis nodosa, Hereditary angioedema , Cystic fibrosis.

C. Pain due to lesions outside the abdomen (Referred pains & neuralgic pains): Here the pain is reported from other sites due to common innervations. Example: Pneumonia, Heart attack, Sub acute bacterial endocarditis, Torsion of testes etc. Pains as a result of some neurogenic lesions are also included in this category. Example: Herpes zoster, Spinal nerve root pains, Tabes dorsalis, TB spine, Abdominal epilepsy, etc.

D. Functional pain: Here, the pain comes without any lesions, mostly due to some psychological causes. Example: Panic disorder, School stress, Somatisation disorder, History of sexual abuse, Irritable bowel syndrome.

E. Pain due to lesions in the urinary tract: Both upper and lower urinary tract lesions cause abdominal pain. Example: Urinary tract infection, Cystitis, Pyelonephritis, Urinary retention, Renal colic, Ureteric colic.

F. Pain due to gynecological and obstetric problems: Even though the gynecological organs are located in the pelvis, most of the lesions present with pain in lower abdomen. Example: Menstrual colic, Ruptured ectopic gestation, Acute salpingitis, Endometriosis, Endometritis, Pelvic inflammatory disease, Torsion of polyp, Pelvic abscess, IUCD pain, Puerperal infection.

G. Causes in children: In children there are some common causes, which are worth mentioning. Example: Babies colic, Lactose intolerance, Milk allergy, Intussusception, Volvolus, Torsion of testes, Accidental swallowing, Streptococcal throat infection, Congenital megacolon, Overfeeding, Food allergy, Aerophagy.

H. Non specific abdominal pain: Here, no immediate cause is found even after history taking and investigations.
In about 35 to 40% of cases of abdominal pain, the cause may not be easily identifiable and hence treated symptomatically. But, if the pain persists along with the appearance of other signs and symptoms that indicate the underlying cause, it should be identified as early as possible to manage the case properly.

Provisional disease diagnosis:

Here the probable condition causing abdominal pain is diagnosed by considering the history, signs and symptoms along with other clinical findings.

Lab investigations:

This includes several diagnostic procedures that can help for the final disease diagnosis. The choice of investigation depends upon the signs and symptoms that indicate a probable condition. The suitable investigation helps to reach a final diagnosis.

Example: Routine blood, Routine urine, Blood biochemistry, Stool examination, X-ray Barium x-ray Ultrasonography, Endoscopy of GIT, CT scan, MRI scan, Gastric acid secretion studies, Laperoscopy, Mucosal biopsy, ECG, Excretory urography, IVP, Exploratory laparotomy etc are some useful investigations.

Final disease diagnosis:

After doing necessary investigations, the disease or the condition causing abdominal pain is diagnosed by correlating with the clinical findings and the history of the patient. In case of a diagnostic dilemma, a team of doctors are involved in the diagnosis and management.