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.

Abdominal Ultrasound

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References