Differentials
Acute mesenteric adenitis
SIGNS / SYMPTOMS
Usually presents in children with a recent history of upper respiratory infection.
Pain in the abdomen is usually diffuse with tenderness not localised to the right lower quadrant.
Guarding may be present, but rigidity is usually absent.
Generalised lymphadenopathy may be noted.
INVESTIGATIONS
There is no specific test to confirm the diagnosis.
Relative lymphocytosis in WBC differential counts is suggestive.
Negative ultrasound or CT findings help exclude other diagnoses.
Viral gastroenteritis
SIGNS / SYMPTOMS
Common in children; caused by viruses, bacteria, or toxin.
Characterised by profuse watery diarrhoea, nausea, and vomiting.
Crampy abdominal pain often precedes the diarrhoea, and no localising signs are present.
If caused by typhoid fever, intestinal perforation may cause localised abdominal pain and/or generalised and rebound tenderness. In this scenario, associated maculopapular rash, inappropriate bradycardia, and leukopenia will differentiate from appendicitis.
INVESTIGATIONS
No specific test unless symptoms of viral gastroenteritis are atypical and you suspect a bacterial or parasitic aetiology
Meckel's diverticulitis
SIGNS / SYMPTOMS
Usually asymptomatic.
Only 20% of the patients present with diverticulitis, and 50% of this group are aged <10 years.[19]
Clinical presentation of diverticulitis is similar to acute appendicitis.
INVESTIGATIONS
Technetium pertechnetate scan may show the enhancement of diverticulum if gastric mucosa is present.
Intussusception
SIGNS / SYMPTOMS
Occurs in young children (aged <2 years).
Sudden onset of colicky pain; between episodes of pain the child is calm.
A sausage-shaped mass may be palpable in the right lower quadrant.
INVESTIGATIONS
Barium enema may demonstrate the intussusception with a coil-spring sign at the point of bowel invagination.
Crohn's disease
SIGNS / SYMPTOMS
Young adult with fever, nausea, vomiting, diarrhoea, right lower quadrant pain, and localised tenderness.
INVESTIGATIONS
CT scan may show intra-abdominal abscess.
Contrast study of the small bowel and colon may show stricture or a series of ulcers and fissures (cobblestone appearance) of mucosa.
Peptic ulcer disease
SIGNS / SYMPTOMS
May or may not have a history of peptic ulcer disease.
Pain is abrupt, severe in intensity, and may be localised to right lower quadrant.
INVESTIGATIONS
Erect CXR and abdominal x-ray may show free air under the diaphragm
Right-sided ureteric stone
SIGNS / SYMPTOMS
Pain is usually colicky in nature and severe in intensity. May be referred to the labia, scrotum, or penis and associated with haematuria.
Fever usually absent.
INVESTIGATIONS
Urinalysis positive for blood.
Leukocytosis usually absent.
Abdominal x-rays or tomogram may show calcified stone.
Pyelography and CT scan without oral and intravenous contrast confirm the diagnosis.
Cholecystitis
SIGNS / SYMPTOMS
Pain and tenderness are usually in the right upper quadrant. In one third of patients the gallbladder can be palpable.[76]
INVESTIGATIONS
Abdominal ultrasound shows thick wall with peri-cholecystic collection, and tenderness is present over gallbladder area (Murphy's sign).
Urinary tract infection
SIGNS / SYMPTOMS
Pain and tenderness is usually in suprapubic area associated with burning micturition.
Acute right-sided pyelonephritis may present with fever, chills, and tenderness at the right costovertebral angle.
INVESTIGATIONS
Urine microscopy and culture confirm presence of bacteria.
Primary peritonitis
SIGNS / SYMPTOMS
Most patients present with abrupt abdominal pain, fever, distension, and rebound tenderness.
History of advanced cirrhosis or nephrosis.
INVESTIGATIONS
CT scan may show fluid in the abdomen.
Peritoneal fluid shows >500/microlitre count and >25% polymorphonuclear leukocytosis.
Pelvic inflammatory disease
SIGNS / SYMPTOMS
Occurs in females usually aged between 20 and 40 years.
Presents with bilateral lower quadrant tenderness, usually within 5 days of the last menstrual period.
Purulent discharge from cervical os.
INVESTIGATIONS
Endocervical swab may confirm the pelvic inflammatory disease due to Chlamydia trachomatis.[77]
Ruptured Graafian follicle (mittelschmerz)
SIGNS / SYMPTOMS
Mid-menstrual cycle, brief period of lower abdominal pain not usually associated with nausea and vomiting and fever.
Tenderness is usually diffuse rather than localised.
INVESTIGATIONS
Clinical diagnosis. No investigation indicated.
Ectopic pregnancy
SIGNS / SYMPTOMS
Female within childbearing age presents with missed menstrual period, right lower quadrant pain, or pelvic pain with some degree of vaginal bleeding or spotting. Cervical motion tenderness may be present on pelvic examination.
INVESTIGATIONS
Human chorionic gonadotrophin hormone level is high in serum and in urine.
Ultrasound reveals presence of mass in fallopian tubes.
Ovarian torsion
SIGNS / SYMPTOMS
Female with right lower quadrant pain. Occasionally presents with mass in the right lower quadrant.
INVESTIGATIONS
Ultrasonography shows ovarian cyst and decreased blood flow.
Caecal diverticulitis
SIGNS / SYMPTOMS
Presents with abdominal pain that localises to the right iliac fossa in 93% of patients.[78] Patients may also have nausea and vomiting, gastrointestinal disturbance, and an elevated white cell count.[78]
INVESTIGATIONS
CT has a sensitivity and specificity of 99% for the diagnosis of acute diverticulitis; it may show an inflamed diverticulum or contrast-filled mass surround by colonic wall thickening, inflammation of the pericolic fat, localised oedema, free fluid or extraluminal air.[78]
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