Doppler ultrasound probe for assessment of blood-flow in oesophageal varices

Novel Endoscopic Therapy for Gastric Varices Using Direct Forward-Viewing Endoscopic Ultrasonography

Gastric varices (GV) carry a high risk of massive hemorrhage because of potential rupture. To reduce the risk associated with GV, patients need to undergo hemostatic and preventive treatment. The objective of this retrospective study was to evaluate the usefulness of a new method, direct forward-viewing endoscopic ultrasonography (DFV-EUS) for the treatment of GV. We performed endoscopic injection sclerotherapy with histoacryl (EIS-HA) using DFV-EUS for GV in four patients. The paracentesis success rate was 75% (3/4). DFV-EUS has a significant advantage for the treatment of GV in that it can show physicians endoscopic and ultrasound views in real time during the delivery of the sclerosant into the GV. However, the proper use of the ultrasound view must be elucidated through further research for safer and more effective therapy. In the presence of distance between the mucosal surface and vascular lumen or when the blood flow site requires puncture as an additional treatment, DFV-EUS might be a good candidate for the treatment of GV. Altogether, EIS-HA with DFV-EUS might be a new therapeutic option for patients with GV.

Balloon-occluded Retrograde Transvenous Obliteration (BRTO): Follow-Up and Postprocedural Imaging

The majority of patients undergoing balloon retrograde transvenous obliteration (BRTO) are decompensated cirrhotic for either bleeding gastric varices (GV) or hepatic encephalopathy. These patients will require close follow-up and assessments pre- and post-BRTO including clinical, laboratory, endoscopic, and imaging evaluations. It is essential that clinicians are aware of the potential benefits and complications that may result from BRTO. These complications may include fever, chest or epigastric pain, hemoglobinuria, transient hypertension, nausea or vomiting, and many more. These complications usually resolve within the first 10 days. Laboratory abnormalities are transient and uncommon. Radiologic and endoscopic follow-up are required including computed tomography (CT), magnetic resonance imaging (MRI), routine upper endoscopy and endoscopic ultrasound (EUS), which are detailed in this review. Patients undergoing BRTO are usually complicated and will require a team approach. This team should include the hepatologist, endoscopist, and interventional radiologist. Understanding and open dialogue are essential in the management of post-BRTO patients. The authors review the possible benefits, potential complications, and the evaluation tools needed to improve outcomes.

The role of Doppler ultrasound in gastrointestinal bleeding

The management of acute gastrointestinal bleeding is the domain of endoscopy. More than half of all episodes of upper gastrointestinal bleeding are attributed to bleeding peptic ulcers, and it is important to assess the risk of recurrent bleeding and to determine the appropriate treatment. However, the visual assessment of lesions (Forrest classification) is not always accurate and shows high interobserver variability (especially for visible vessels at the ulcer base, associated with a high rate of re-bleeding). Doppler ultrasound was thus introduced, and several studies have demonstrated that, with Doppler examination, these vessels can be identified. Doppler ultrasound is also used to monitor the effects of endoscopic therapy. In a prospective randomized trial, Doppler ultrasound proved superior to the Forrest classification. Treatment based on this technique resulted in significantly lower rates of re-bleeding and mortality. The Doppler classification may be able to contribute to a safer and more cost-effective management of patients with acute peptic ulcer bleeding.

Renal effects of TAPP, a highly selective mu-opioid agonist

1. The effect of i.v. administration of TAPP, a highly selective and exclusively peripherally-acting mu-opioid receptor agonist, on urine output, urinary sodium, potassium and cyclic GMP, and on plasma immunoreactive atrial natriuretic factor (IR-ANF) levels was studied in conscious normally hydrated female rats (200-250 g). 2. TAPP treatment produced a significant dose-dependent increase of urine output and urinary sodium, potassium and cyclic GMP excretion during the first hour. The highest TAPP dose used (2.5 mg kg-1. body weight) elicited a 10 fold elevation of urine output from 0.23 +/- 0.06 ml h-1 to 2.5 +/- 0.3 ml h-1 (n = 18) accompanied by augmented sodium [from 17.0 +/- 4.7 mu Eq h-1 to 79 +/- 12.7 mu Eq h-1, n = 18 (P < 0.001)], potassium [from 9.5 +/- 2.5 mu Eq h-1 to 39.4 +/- 6.6 mu Eq h-1, n = 18 (P < 0.005)], and cyclic GMP excretion [from 191 +/- 21 pmol h-1 to 1340 +/- 322 pmol h-1, n = 18 (P < 0.001)]. Plasma IR-ANF rose from 22 +/- 4 pg ml-1 to 508 +/- 22 pg ml-1 (n = 18) (P < 0.001) 5 min after administration of TAPP (2500 micrograms kg-1). 3. TAPP lowered systemic blood pressure, also in a dose-related manner, 1-5 min after injection. This decrease in blood pressure was transient and did not last more than 10 min. 4. Pretreatment with the opioid antagonist naloxone (0.8 mg per rat) abolished the diuretic, natriuretic and kaliuretic effect of TAPP (250 micrograms kg-1); urine output dropped from 1.16 +/- 0.15 ml h-1, n = 12, to the control value of 0.15 +/- 0.06 ml h-1, n = 12 (P < 0.001), sodium excretion fell from 57.5 +/- 11 mu Eq h-1, to 21.3 +/- 8.5 mu Eq h-1, n = 12 (P < 0.001), and potassium excretion decreased from 45.4 +/- 9.7 mu Eq h-1, n = 12, to 16.1 +/- 7.0 mu Eq h-1, (P < 0.001). 5. Pretreatment with anti-ANF serum (0.4 ml) abolished the diuretic effect of TAPP: urine output diminished significantly from 1.93 +/- 0.28 to 0.88 +/- 0.29 ml h-1 (P < 0.01) (n = 6). The TAPP-induced diuretic action, increased sodium/potassium excretion and elevated urinary cyclic GMP levels were also reversed by anti-ANF antibodies. 6. Since TAPP is totally unable to cross the blood-brain barrier, the ensemble of these observations led to the conclusion that the diuretic, natriuretic, kaliuretic and hypotensive effects produced by this mu-opioid agonist through interaction with peripheral mu-opioid receptors occur via ANF release.

Haemodynamic assessment

The degree of portal hypertension and its haemodynamic complications can be easily determined. However, the interpretation of these values is not entirely clear and further clinical and experimental studies are needed to explain why some patients with portal hypertension bleed from oesophageal varices while others do not.

Colonization by Helicobacter pylori and its relationship to histological changes in the gastric mucosa in portal hypertension

In order to investigate the relationship between Helicobacter pylori infection of the gastric mucosa and mucosal changes in portal hypertension, gastric fundic and antral biopsies were obtained from 66 patients with portal hypertension and 49 controls with non-ulcer dyspepsia (NUD). Gastric mucosa from portal hypertensive patients exhibited typical vascular dilatation and congestion, while mild dilatation of lamina propria blood vessels was not uncommon in NUD patients with histological evidence of gastritis. Colonization of the gastric mucosa by H. pylori infection was significantly less in portal hypertension (51.5%) compared to controls (75.5%; P < 0.01). The difference was more apparent in patients with marked vascular dilatation (18.8% colonization) compared to patients with minimal vascular dilatation (66.7%). H. pylori infection was significantly associated with active superficial gastritis (P < 0.001), and with atrophic gastritis (P < 0.001), in both study groups. H. pylori-negative superficial gastritis was significantly more common in portal hypertension (25/66 patients) than in controls (7/49; P < 0.05). H. pylori infection was not more common in patients who had undergone repeated sclerotherapy. The results suggest that the gastric mucosa of portal hypertension does not provide a hospitable environment for H. pylori colonization, particularly when mucosal congestion is marked. H. pylori infection does not add significantly to the gastropathy of portal hypertension.

The endoscopic Doppler: its value in evaluating gastroduodenal ulcers after hemorrhage and as an instrument of control of endoscopic injection therapy

In this prospective study of 80 patients with active bleeding from the gastrointestinal tract a Doppler ultrasonographic investigation of the gastroduodenal ulcers was performed, in addition to immediate endoscopic examination. Admitted to this study were ulcers with the stigmata of acute bleeding, such as a visible blood vessel in the ulcer floor, a blood clot, or a black base and Forrest III lesions. In 52 patients Doppler ultrasonography was able to document unequivocally a superficial blood vessel. Complete agreement of endoscopic and Doppler results was obtained in only 49% of the cases. When a blood vessel was positively identified, local injection of epinephrine and polidocanol was carried out. Thereupon, in the further course, the acoustic signal was shifted into deeper regions or disappeared entirely. In 8% of the cases initial sclerosing was followed by a rebleed, which was again treated by injection therapy. None of the patients died of their GI hemorrhage. Endoscopic Doppler ultrasonography is a new and effective procedure that enables objectification of the endoscopic findings. It identifies the indication for proceeding to operative endoscopy and can monitor the effectiveness of the latter.

The 'mosaic-like' pattern of portal hypertensive gastric mucosa after variceal eradication by sclerotherapy

The 'mosaic-like' pattern of portal hypertensive gastric mucosa has been evaluated endoscopically in 38 patients referred for elective sclerotherapy, before the first session, after the complete eradication of varices and six months later. Of 38 patients studied, 18 patients exhibited mild, and 20 patients exhibited negative, findings of congestive gastropathy prior to sclerotherapy. Seventeen and 18 patients, respectively, developed aggravated changes of congestive gastropathy after the completion of sclerotherapy (P = 0.003). We consider that obliteration of varices by means of endoscopic sclerotherapy influences the development of gastric congestion changes in the majority of patients. However, further studies are required to relate the direction of blood flow in the portal system as well as the level of portal pressure with the congestive gastropathy findings in such patients.

Endoscopic ultrasound probes

Ultrasound probes are being developed as alternatives to dedicated ultrasound endoscopes. These probes have been designed to pass through the instrument channel of ordinary fiberoptic or video endoscopes. We have developed a 20-MHz mechanical linear probe for use within the upper gastrointestinal tract, pancreatic duct, biliary tree, and colon. Rotational mechanical sector scanning probes as well as phased array probes are also being developed. Ultrasound probes are best used for high resolution imaging of focal endoscopically visible lesions. Endoscopic visualization enables direction of the probe to the lesion of interest. Unlike dedicated ultrasound endoscopes, ultrasound probes do not screen large areas of tissue and do not have deep penetration. Ongoing research will help define the indications for use of these probes and should lead to further refinements in their design.

Pathophysiology and epidemiology of portal hypertension

Changes in portal pressure are regulated by changes in hepatic vascular resistance, which is normally under neurohumoral control, and portal tributary blood flow. Two theories on the pathophysiology of portal hypertension have been proposed: the 'backward flow' theory, in which portal hypertension is attributable to increased resistance to portal venous flow, and the 'forward flow' theory, in which increased splanchnic blood flow maintains portal hypertension despite extreme portal-systemic shunting. The sinusoidal abnormalities caused by an accumulation of collagen in the perisinusoidal space of Disse may induce increased resistance to blood flow in various pathological conditions of the liver. Non-cirrhotic portal hypertension results from not only relatively uncommon disorders prevalent mainly in Asia and tropical countries, but also from acute and chronic phases of relatively common liver diseases. Systemic hyperdynamic circulation, characterised by an increased cardiac output and a reduced peripheral vascular resistance, and splanchnic hyperaemia may develop as consequences of portal hypertension. Although the mechanisms of these changes are not clearly understood, portal-systemic shunting as well as some vasoactive substances, including prostaglandins, may be involved. The erosive and eruptive mechanisms are the two potential explanations for variceal bleeding. In the latter, pressure should not be viewed in isolation and other additive factors such as variceal size may be involved. Several new techniques of measuring variceal pressure and blood flow may improve understanding of the actual pathophysiology of variceal bleeding. Renal haemodynamic alterations secondary to the systemic circulatory changes produced by portal hypertension may occur. The geographical pattern of prevalence in disorders associated with portal hypertension is briefly described in this paper.

Assessment of the effect of respiration on the esophageal variceal blood flow using transesophageal real-time two-dimensional Doppler echography

The effect of spontaneous respiration on esophageal variceal flow was evaluated using 5 MHz color flow Doppler echography. Twenty-one patients with esophageal varices, of whom 19 had liver cirrhosis (95%), were examined with a convex array transesophageal transducer. The direction and velocity of the variceal flow during inhalation and exhalation could be inferred from the color, its brightness or the Doppler time-velocity spectrum. The mean intravariceal flow velocity was significantly higher during inhalation (20.6 cm per sec) than in exhalation (11.5 cm per sec; p less than 0.01). The direction of intravariceal flow at any given point did not change throughout the respiratory cycle. However, a combination of real-time color flow imaging and the doppler time-velocity spectrum revealed that, when the sampling point was near the peak of the curve of the varix, the spectrum falsely indicated reversal of direction between inhalation and exhalation. This semiinvasive method, which yields anatomical and physiological information simultaneously, appears to be very useful for the study of variceal flow.

Usefulness of manometric assessment of varices in maintenance sclerotherapy. A controlled trial

In a prospective controlled study, 68 patients undergoing maintenance sclerotherapy were randomized to have intravariceal sclerotherapy based on either manometric assessment (n = 35) or visual assessment (controls, n = 33) of varix patency. For manometric assessment, a perfused variceal needle punctured each variceal column and, if low pressures fluctuating with respiration were obtained, the varix was injected. Control patients had patent varices injected based on visual assessment alone. During a mean follow-up of 13 mo (range 4-16 mo), 1 manometrically assessed patient bled once (0.002 bleeds/patient month) and 7 visually assessed patients bled 14 times from varices (0.03 bleeds/patient-month) (p less than 0.05). Two and nine episodes of ulceration occurred in manometric and visually assessed patients, respectively, (p less than 0.05). Varices were obliterated (i.e., disappeared) in 11 patients undergoing manometric assessment and in 2 patients undergoing visual assessment (p less than 0.01). Comparing results of visual and manometric assessment within "manometric" patients showed a consistent 25% error rate in diagnosing patency or thrombosis by visual assessment. Manometric assessment of varices during maintenance sclerotherapy reduces rebleeding and ulceration to very low levels.

Superior portosystemic collateral circulation estimated by azygos blood flow in patients with cirrhosis. Lack of correlation with oesophageal varices and gastrointestinal bleeding. Effect of propranolol

In patients with cirrhosis, superior portosystemic collateral circulation was evaluated by the continuous thermodilution method in the azygos vein. Azygos blood flow was 5 times higher in a group of patients with cirrhosis (alcoholic in 27, cryptogenic in 8, post-hepatitic in 2 and primary biliary cirrhosis in 1), than in a group of patients without portal hypertension (steatosis in 2, granulomatous hepatitis in 2, persistent chronic hepatitis in 2 and Hodgkin's disease in 1). Azygos blood flow was not different in cirrhotic patients with no visible, in those with small-sized, and in those with large sized oesophageal varices. Azygos blood flow was not different in cirrhotic patients with and without a previous episode of gastrointestinal bleeding. Fifteen min after intravenous administration of 15 mg of propranolol, azygos blood flow significantly decreased whereas azygos blood flow did not change after placebo. The decrease in azygos blood flow was significantly more marked than the reduction in cardiac output. It is concluded that superior portosystemic collateral blood flow is elevated in patients with cirrhosis and that the reduction in this collateral circulation might explain the efficiency of propranolol in the prevention of recurrent gastrointestinal bleeding.

Perforating veins and blood flow in oesophageal varices

Blood-flow patterns in oesophageal varices were studied by doppler ultrasound (18 patients) and injection radiography (34 patients). Both techniques demonstrated that blood flow is not always in the expected cephalad direction but is often towards the stomach. Doppler studies indicated that there are functioning perforating veins joining oesophageal varices to the peri-oesophageal veins, particularly at the lower end of the oesophagus. The presence of these perforators was confirmed by intravariceal injection radiography and also at necropsy. The turbulent flow caused by these veins may explain why variceal rupture commonly occurs just above the gastrooesophageal junction. Successful treatment of oesophageal varices with the minimum of sclerotherapy treatments may depend on early obliteration of the incompetent perforating veins.