axr
Table of Contents
plain abdominal X-ray (AXR)
introduction
- plain AXR is generally avoided unless there is a specific indication which outweighs the radiation risks given the radiation dose is equivalent to ~ 20 chest XRays
- when looking for small bowel obstruction, an erect and supine film is requested, but these are only 50-60% sensitive
- when looking for possible perforated viscus, an erect CXR should also be requested to look for free gas under the diaphragm
normal small bowel
- rule of threes:
- wall thickness < 3mm
- valvulae conniventes < 3mm thick
- small bowel diameter < 3cm
- less than 3 air-fluid levels per AXR
signs of small bowel obstruction
- multiple air fluid levels on erect AXR
- absence of colonic distention
- stepladder appearance of small bowel loops at different heights
- string of pearls indicating trapped air in valvulae conniventes
signs of large bowel obstruction
- dilated colon (>6cm), especially caecum (> 9cm)
- NB. dilation more than 3cm more than these upper limits starts to increase risk of perforation
- air fluid levels on erect AXR, esp. distal to hepatic flexure
- 25% have small bowel dilatation due to reflux of gas through ileocaecal valve
- NB. non-mechanical causes include toxic megacolon and paralytic ileus
calcifications on AXR
- 20% of gallstones are visible on AXR due to calcification
- calcified wall of gallbladder porcelain gallbladder indicates chronic inflammation and a high risk of neoplasia, hence are usually resected
- pancreatic calcifications are pathognomonic of chronic pancreatitis
- NB. adenocarcinoma of pancreas almost never calcifies, although other unusual tumours may calcify
- calcifications are commonly seen in the arterial tree (eg. aorta, iliac, renal, splenic arteries)
- 80% of ureteric calculi are radio-opaque but CT KUB is a much more sensitive test than plain AXR to detect these, however, plain AXR is useful to monitor progress of larger ureteric stones
- 10% of patients with appendicitis have a calcified faecolith (appendicolith) in the RIF, and this increases risk of early rupture.
- hepatic or splenic calcifications:
- small punctate calcifications in the liver and spleen may indicate past histoplasmosis infection
- spiculated, sunburst calcification in the liver is diagnostic of haemangioma
- other causes of calcifications in the liver:
- PH granulomatous disease
- old trauma
- metastatic disease (eg. colorectal cancer (bowel cancer)
- primary hepatocellular carcinoma
- other causes of calcifications in the spleen:
- PH granulomatous disease
- old trauma
- metastatic disease (eg. colorectal cancer (bowel cancer)
- benign primary lesions such as benign cysts, haemangiomata
- calcification of adrenal glands:
- old haematoma
- old infection
- NB. calcification is unusual in adrenal tumours
- calcification throughout abdominal wall:
- generalised calcification states (eg. hypercalcaemia)
- abdo. wall infarction (eg. nematodes)
- muscle inflammation (eg. dermatomyositis)
- calcification in the pelvic region
- calcifications within the pelvic veins (phleboliths) are common and of no importance but can be mistaken for ureteric calculi
- arterial wall calcification in iliac arteries
- ureteric calculus at VUJ
- bladder stones
- calcified material within dermoid cysts (eg. teeth)
- fetus in pregnant patients
axr.txt · Last modified: 2013/08/15 02:42 by 127.0.0.1