Imaging Uganda/Africa

Portal hypertension

Introduction

Portal hypertension is a clinical syndrome defined by a pathological increase in the portal venous pressure, with the hepatic venous pressure gradient (HVPG) exceeding 5 mmHg. Ultrasound plays a crucial role in the non-invasive assessment of portal hypertension, providing both direct and indirect signs of this condition.

Clinical Presentation

Patients with portal hypertension may present with:

  • Ascites - The most common clinical manifestation
  • Gastroesophageal varices - With risk of life-threatening hemorrhage
  • Splenomegaly - Due to venous congestion
  • Hepatic encephalopathy - From portosystemic shunting
  • Caput medusae - Dilated periumbilical veins
Key Point: Ultrasound is often the first imaging modality employed when portal hypertension is suspected, due to its non-invasive nature, lack of radiation, and ability to provide both anatomical and hemodynamic information.

Ultrasound findings

Direct Signs

  • Portal vein diameter >13 mm (measured at the hepatic hilum during quiet respiration)
  • Loss of respiratory phasicity in portal vein Doppler waveform
  • Portal vein flow velocity <16 cm/s
  • Hepatofugal flow (reversed portal vein flow)
  • Portal vein thrombosis (partial or complete)

Indirect Signs

  • Splenomegaly (spleen length >12 cm)
  • Portosystemic collaterals (varices):
    • Paraumbilical vein (recanalized ligamentum teres)
    • Coronary-gastric varices
    • Splenorenal shunts
  • Cavernous transformation of the portal vein (chronic thrombosis)
  • Ascites
  • Liver parenchymal changes consistent with cirrhosis
Portal vein Doppler ultrasound

1. Doppler findings

  • Doppler ultrasound showing hepatofugal flow in the portal vein
Portal vein dilatation

2. Dilatation of portal vein (calipers)

  • B-Mode ultrasound showing main portal vein diameter of 15.1 millimeters.
  • This is an indirect finding of portal hypertension.
Splenic vein dilatation

2. Dilatation of splenic vein (calipers)

  • Splenic vein dilation, collaterals at the splenic hilum, and Gamna-Gandy bodies in the splenic parenchyma.
Portal vein thrombosis

2. Portal vein thrombosis

  • Echogenic contents in the portal vein lumen
  • Absence of flow on doppler
  • Distension of the portal vein and its tributaries

Doppler Ultrasound Parameters

Parameter Normal Value Portal Hypertension
Portal vein diameter <13 mm >13 mm
Portal vein velocity 16-40 cm/s <16 cm/s
Congestion index (Area/Velocity) <0.07 >0.07
Flow direction Hepatopetal Hepatofugal in advanced cases

Collateral Pathways

Ultrasound can identify several portosystemic collateral pathways that develop in portal hypertension:

  1. Gastroesophageal varices - Most clinically significant due to bleeding risk
  2. Paraumbilical vein - Recanalized ligamentum teres, seen as tortuous vein from left portal vein to abdominal wall
  3. Splenorenal shunts - Between splenic vein and left renal vein
  4. Hemorrhoidal plexus - Between superior and middle/inferior rectal veins
  5. Retroperitoneal collaterals - Between mesenteric veins and retroperitoneal veins
.

Conclusion

Ultrasound is an invaluable tool in the evaluation of portal hypertension, providing both anatomical and hemodynamic information. While it cannot replace direct pressure measurements, it offers a non-invasive method for diagnosis, assessment of complications, and monitoring of disease progression. The combination of B-mode imaging and Doppler evaluation allows comprehensive assessment of the portal venous system and associated collateral circulation.

References

  1. Berzigotti A, et al. Ultrasound in portal hypertension - part 1. Ultraschall Med. 2021;42(1):34-57.
  2. Dietrich CF, et al. Ultrasound in portal hypertension - part 2. Ultraschall Med. 2021;42(2):128-161.
  3. European Association for the Study of the Liver. EASL Clinical Practice Guidelines for the management of patients with portal hypertension. J Hepatol. 2018;69(4):716-735.
  4. American College of Radiology. ACR Appropriateness Criteria® for Radiologic Management of Portal Hypertension.