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ULTRASOUND
AbdomenDemonstration data

Abdominal Ultrasound

Abdominal ultrasound is a first-line, radiation-free imaging test for evaluating the solid and hollow organs of the upper abdomen. It is the preferred initial study for suspected hepatobiliary disease, right upper quadrant pain, jaundice, and screening for ascites or abdominal masses. Its portability, low cost, and real-time capability make it invaluable in acute and outpatient settings, though it is operator-dependent and limited by bowel gas and body habitus.

Indications

  • Right upper quadrant pain and suspected cholelithiasis or cholecystitis
  • Jaundice or abnormal liver function tests to assess for biliary obstruction
  • Hepatomegaly, suspected cirrhosis, or characterization of a liver lesion
  • Screening and surveillance for hepatocellular carcinoma in chronic liver disease
  • Suspected ascites, portal hypertension, or splenomegaly
  • Palpable abdominal mass or abdominal aortic aneurysm screening
  • Renal evaluation for hydronephrosis, stones, or masses
  • Guidance for paracentesis or organ biopsy

Contraindications & Cautions

  • No absolute contraindications; ultrasound uses no ionizing radiation and is safe in pregnancy and children
  • Relative limitation: overlying bowel gas obscures the pancreas, aorta, and retroperitoneum
  • Large body habitus reduces penetration and image quality
  • Recent barium studies degrade acoustic windows
  • Open wounds, dressings, or surgical drains may prevent adequate transducer contact
  • Follow ALARA principles for thermal and mechanical index, particularly with Doppler

Patient Preparation

  • Fast for 6-8 hours before the study to distend the gallbladder and reduce bowel gas
  • Water may be permitted to maintain hydration and provide a gastric window for the pancreas
  • No formal consent required for diagnostic scanning
  • Supine positioning with optional left and right lateral decubitus and erect views
  • Deep inspiration and breath-hold to lower the liver and kidneys below the costal margin
  • Explain the need to apply pressure and warm gel to the patient

Technique & Parameters

  • Curvilinear low-frequency transducer (2-5 MHz) for deep structures; higher frequency for superficial evaluation
  • Systematic survey of liver in sagittal, transverse, and subcostal oblique planes with hepatic and portal vein Doppler
  • Gallbladder assessed fasting in supine and left lateral decubitus; measure wall thickness and evaluate for stones and sonographic Murphy sign
  • Common bile duct measured at the porta hepatis (normal up to 6-7 mm, increasing with age and post-cholecystectomy)
  • Pancreas imaged in the epigastrium using the left lobe of liver or fluid-filled stomach as a window
  • Kidneys measured in long axis (normal 9-12 cm) with assessment of cortical echogenicity and corticomedullary differentiation
  • Spleen measured in the coronal plane (normal up to 12-13 cm), aorta and IVC assessed for caliber and aneurysm
  • Color and spectral Doppler for portal vein patency and direction of flow

Systematic Review

  • Liver: size, contour, echotexture, focal lesions, and vascular patency
  • Gallbladder: stones, sludge, wall thickness, pericholecystic fluid, Murphy sign
  • Biliary tree: intrahepatic and extrahepatic duct caliber, common bile duct measurement
  • Pancreas: size, echogenicity, ductal dilatation, focal mass (limited by gas)
  • Spleen: size and echotexture, accessory spleen
  • Kidneys: size, cortical thickness, echogenicity, hydronephrosis, calculi, masses
  • Aorta and IVC: caliber, aneurysm, thrombus
  • Peritoneal spaces: free fluid in Morison pouch, paracolic gutters, pelvis

Key Findings & Significance

  • Increased liver echogenicity with posterior beam attenuation indicates hepatic steatosis
  • Coarse nodular liver surface with caudate hypertrophy suggests cirrhosis
  • Echogenic foci with posterior acoustic shadowing that move with gravity indicate gallstones
  • Gallbladder wall thickening >3 mm with pericholecystic fluid and positive Murphy sign suggests acute cholecystitis
  • Intrahepatic duct dilatation and a dilated CBD indicate biliary obstruction; level determines cause
  • Hydronephrosis indicates urinary tract obstruction; echogenic shadowing focus indicates a stone
  • Anechoic free fluid in dependent spaces indicates ascites or hemoperitoneum

Differential Considerations

  • Diffuse increased liver echogenicity: steatosis, chronic hepatitis, cirrhosis, infiltration
  • Cystic liver lesion: simple cyst, hydatid, biliary hamartoma, abscess, cystic metastasis
  • Solid liver lesion: hemangioma, focal nodular hyperplasia, adenoma, HCC, metastasis
  • Dilated CBD: choledocholithiasis, periampullary or pancreatic head tumor, stricture, cholangitis
  • Gallbladder wall thickening: cholecystitis, hepatitis, hypoalbuminemia, heart failure, adenomyomatosis
  • Hypoechoic renal lesion: cyst, angiomyolipoma (usually echogenic), renal cell carcinoma, complex cyst

Pearls & Pitfalls

  • Always scan the gallbladder in two positions to confirm stone mobility versus a fixed polyp
  • Reverberation and edge shadowing artifacts can mimic pathology; adjust the scan angle
  • The pancreatic tail and retroperitoneum are commonly obscured by gas and are frequent blind spots
  • A contracted, stone-filled gallbladder with the wall-echo-shadow sign is easily missed
  • Twinkle artifact on Doppler helps confirm renal calculi
  • Comet-tail artifacts in the gallbladder wall suggest adenomyomatosis, a benign entity
  • Do not mistake the duodenum or colon for a pancreatic or renal mass; observe peristalsis

Structured Report

  • State clinical indication and whether the patient was fasting
  • Report each organ systematically with measurements: liver, gallbladder, biliary tree, pancreas, spleen, kidneys, aorta
  • Describe focal lesions with size, location, echogenicity, and vascularity
  • Note presence and distribution of free fluid
  • Document technical limitations such as bowel gas or body habitus
  • Impression: concise summary with the leading diagnosis and recommended follow-up such as CT, MRI, or MRCP where indicated

References

  • ACR-AIUM-SRU Practice Parameter for the Performance of an Ultrasound Examination of the Abdomen and Retroperitoneum
  • Rumack CM, Levine D. Diagnostic Ultrasound, 5th edition
  • ACR Appropriateness Criteria: Right Upper Quadrant Pain
  • Society of Radiologists in Ultrasound consensus on gallbladder and biliary imaging

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.