Investigations
1st investigations to order
FBC with differential
Test
Polymorphonuclear leukocytosis is present in acute diverticulitis.[55] Consider diverticulitis in older patients with abdominal pain and leukocytosis, because the presentation can be atypical in this group. FBC results should be considered at the first encounter with a patient when diverticulitis is suspected.
Result
polymorphonuclear leukocytosis
urea and electrolytes
Test
Assesses kidney function and helps to determine whether a contrast CT can be performed.[39]
Result
uraemia, elevated creatinine
C-reactive protein
Test
Identifies inflammation.
Result
consider alternative diagnoses if the inflammatory markers are not raised[39]
Investigations to consider
contrast CT scan of abdomen
Test
Request a contrast CT scan of the abdomen as the imaging modality of choice for a patient with suspected acute diverticulitis and raised inflammatory markers.[39][48]
Findings in patients with acute diverticulitis may show diverticulosis with associated colon wall thickening, fat stranding, phlegmon, extraluminal gas, abscess formation, or intra-abdominal free fluid.[6]
CT may also exclude other diagnoses, such as ovarian pathology or leaking aortic or iliac aneurysm.[6]
Result
thickening of bowel wall, mass, abscess, streaky mesenteric fat; may show gas in the bladder in cases of fistula
non-contrast CT scan of abdomen
Test
Consider a non-contrast CT if a CT with contrast is contraindicated.[39] Discuss with the radiology team.
Result
thickening of bowel wall, mass, abscess, streaky mesenteric fat; may show gas in the bladder in cases of fistula
abdominal ultrasound (graded-compression)
Test
Consider an abdominal ultrasound if a CT with contrast is contraindicated.[39] Discuss with the radiology team.
Result
signs of abscess, perforation, obstruction
MRI
Test
Consider as an alternative if CT with contrast is contraindicated.[39] Discuss with the radiology team.
Result
thickening of bowel wall, mass, abscess, streaky mesenteric fat; may show gas in the bladder in cases of fistula
chest x-ray
Test
Use to assess for possible pneumoperitoneum in people with suspected perforation.
Result
normal, or free air under diaphragm if perforation
colonoscopy
Test
Use when diagnosis of diverticular disease is unclear and cancer or bowel ischaemia is suspected. Can be used for accurate diagnosis in acute bleeding. However, the US guidelines suggest lower gastrointestinal (GI) endoscopy on a non-urgent basis after 24 hours following presentation.[57] Patients with a major bleed should be admitted to hospital for colonoscopy.[56]
Result
single, multiple, or scattered diverticula, with or without acute mucosal inflammation; in acute bleeding, might identify source of segmental bleeding or proximal extent of bleeding; if co-existent, mucosal pathology such as ischaemia, inflammatory bowel disease, and neoplasm may be seen
sigmoidoscopy
Test
Use when diagnosis of diverticular disease is unclear and cancer or bowel ischaemia is suspected. Can be used for accurate diagnosis in acute bleeding.[58] However, the US guidelines suggest lower GI endoscopy on a non-urgent basis after 24 hours following presentation.[57]
Result
mucosal pathology such as ischaemia, inflammatory bowel disease, and neoplasm
CT angiogram
Test
For haemodynamically unstable patients or those with a shock index (heart rate/systolic blood pressure) of >1 after initial resuscitation, use CT angiography (CTA) to locate the site of blood loss, prior to endoscopic or radiological therapy.[56]
Result
aetiology of bleeding identified
isotope-labelled red blood cell nuclear scan
Test
Discuss with a radiologist.
Rarely used in acute bleeding (as largely been superseded by CTA). May be considered if bleeding is too profuse to enable identification using colonoscopy.
Result
aetiology of bleeding identified
diagnostic laparoscopy
Test
Typically diagnostic laparoscopy is not a recommended investigation to diagnose colonic diverticular disease.
Has a role if the primary diagnosis remains unclear after investigations and imaging, and if other investigations, such as CT scan, show complications of diverticular disease (e.g., intra-abdominal collections, abscess, suspicious mass or fistulation). Laparoscopy may also provide therapeutic options.
Result
diverticuli, abscess, perforation, obstruction, fistula
blood culture
Test
Consider in:
Patients with signs or symptoms of systemic sepsis
Patients who are severely ill
Patients who have complications (e.g., perforation, fistula, phlegmon).
Result
usually gram negative rods, and anaerobic bacteria; obtain prior to administration of antibiotics
ABG and serum lactate
Test
Consider in:
Patients with signs or symptoms of systemic sepsis
Patients who are severely ill.
Result
acidosis, elevated serum lactate in patients with sepsis
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