Paediatric CT dose: a multicentre audit of subspecialty practice in Australia and New Zealand.

OBJECTIVES: To evaluate paediatric CT dosimetry in Australia and New Zealand and calculate size-specific dose estimates (SSDEs) for chest and abdominal examinations. METHODS: Eight hospitals provided data from 12 CT systems for 1462 CTs in children aged 0-15. Imaging data were recorded for eight examinations: head (trauma, shunt), temporal bone, paranasal sinuses, chest (mass) and chest HRCT (high-resolution CT), and abdomen/pelvis (mass/inflammation). Dose data for cranial examinations were categorised by age and SSDEs by lateral dimension. Diagnostic reference ranges (DRRs) were defined by the 25th and 75th percentiles. Centralised image quality assessment was not undertaken. RESULTS: DRRs for 201 abdominopelvic SSDEs were: 2.8-4.7, 3.6-11.5, 8.5-15.0, 7.6-15, and 10.6-16.2 for the <15 cm, 15-19 cm, 20-24 cm, 25-29 cm and >30 cm groups, respectively. For 147 chest examinations using these body width categories, SSDE DRRs were 2.0-4.4, 3.3-7.9, 4.0-9.4, 4.5-12, and 6.5-12. Kilovoltage peak (kVp), but not AEC or IR, was associated with SSDE (parameter estimate [standard error]: 0.12 (0.03); p < 0.0001). CONCLUSIONS: Australian and New Zealand paediatric CT DRRs and abdominal SSDEs are comparable to international data. SSDEs for chest examinations are proposed. Dose variations could be reduced by adjusting kVp. KEY POINTS: • SSDEs can be calculated for all patients, CT systems, and practices • Kilovoltage peak (kVp) has the greatest association with dose in similar-sized patients • Paediatric DRRs for CT are now available for use internationally.

A randomized trial of high-dose vitamin D2 in relapsing-remitting multiple sclerosis.

OBJECTIVE: Higher latitude, lower ultraviolet exposure, and lower serum 25-hydroxyvitamin D (25OHD) correlate with higher multiple sclerosis (MS) prevalence, relapse rate, and mortality. We therefore evaluated the effects of high-dose vitamin D2 (D2) in MS. METHODS: Adults with clinically active relapsing-remitting MS (RRMS) were randomized to 6 months' double-blind placebo-controlled high-dose vitamin D2, 6,000 IU capsules, dose adjusted empirically aiming for a serum 25OHD 130-175 nM. All received daily low-dose (1,000 IU) D2 to prevent deficiency. Brain MRIs were performed at baseline, 4, 5, and 6 months. Primary endpoints were the cumulative number of new gadolinium-enhancing lesions and change in the total volume of T2 lesions. Secondary endpoints were Expanded Disability Status Scale (EDSS) score and relapses. RESULTS: Twenty-three people were randomized, of whom 19 were on established interferon or glatiramer acetate (Copaxone) treatment. Median 25OHD rose from 54 to 69 nM (low-dose D2) vs 59 to 120 nM (high-dose D2) (p = 0.002). No significant treatment differences were detected in the primary MRI endpoints. Exit EDSS, after adjustment for entry EDSS, was higher following high-dose D2 than following low-dose D2 (p = 0.05). There were 4 relapses with high-dose D2 vs none with low-dose D2 (p = 0.04). CONCLUSION: We did not find a therapeutic advantage in RRMS for high-dose D2 over low-dose D2 supplementation. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that high-dose vitamin D2 (targeting 25OHD 130-175 nM), compared to low-dose supplementation (1,000 IU/d), was not effective in reducing MRI lesions in patients with RRMS.

Value and limitations of diffusion-weighted imaging in grading and diagnosis of pediatric posterior fossa tumors.

DWI reportedly accurately differentiates pediatric posterior fossa tumors, but anecdotal experience suggests limitations. In 3 years, medulloblastoma and JPA were differentiated by DWI alone in 23/26 cases (88%). Ependymoma (n = 5) could not be reliably differentiated from medulloblastoma or JPA. A trend toward increased diffusion restriction in higher grade tumors (1/14 grade I, 7%; 9/12 grade IV, 75%) had too much overlap to predict the grade of individual cases. The overlap in ADC between tumor types appeared partly due to technical factors (in small, heterogeneous, calcific, or hemorrhagic tumors) but also likely reflected true histologic variability, given that our 3 overlap cases included a desmoplastic medulloblastoma, an anaplastic ependymoma, and a JPA with restricted diffusion in its nodule. Simple structural features (macrocystic tumor, location off midline) aided in distinguishing JPA from the other tumors in these cases.

Practice MRI: reducing the need for sedation and general anaesthesia in children undergoing MRI.

The aim of this study was to evaluate the effectiveness of a practice magnetic resonance unit, in preparing children to undergo magnetic resonance procedures without general anaesthesia (GA) or sedation. The records of children who attended the practice MRI between February 2002 and April 2004 were retrospectively reviewed. Each record was assessed as to whether the child had passed or failed the practice MRI intervention. Those children who were considered to have passed and were proceeded to a clinical non-GA MRI had the report of the clinical scan reviewed. If the scan had been reported as non-diagnostic because of movement artefact it was classified as a failed scan, otherwise it was considered a pass. One hundred and thirty-four children undertook a practice MRI (age range 4.1-16.1 years, median age 7.7 years, 47% boys) and 120/134 (90%) passed the practice session. In all, 117/120 (98%) subsequently had a clinical non-GA MRI and 110/117 (94%) passed (median age 7.8 years, 47% boys). Preparation is a safe and effective method to reduce the need for sedation and GA in children undergoing a clinical MRI scan. It provides a positive medical experience for children, parents and staff, and results in cost savings for the hospital.

Complementary use of radiological skeletal survey and bone scintigraphy in detection of bony injuries in suspected child abuse.

AIM: To compare the effectiveness of radiological skeletal survey and bone scintigraphy for the detection of bony injuries in cases of suspected child abuse. METHODS: All cases with a discharge diagnosis of child abuse that presented to the Royal Children's Hospital between 1989 and 1998 were retrieved, and those children that had undergone both skeletal survey and bone scintigraphy (radioisotope bone scan) within a 48 hour period were included in this study. Both examinations followed rigid departmental protocols and protocols remained identical throughout the timeframe of the study. The reports of the skeletal surveys and bone scans were retrospectively reviewed by a paediatric radiology fellow and consultant paediatric radiologist. RESULTS: The total number of bony injuries identified was 124 in 30 children. Of these, 64 were identified on bone scan and 77 on skeletal survey. Rib fractures represented 60/124 (48%) of the bony injuries and were present in 16/30 children (53%), of which 62.5% had multiple rib fractures. Excluding rib fractures, there were 64 (52%) bony injuries, of which 33% were seen on both imaging modalities, 44% were seen on skeletal survey only, and 25% were seen on bone scans alone. Metaphyseal lesions typical of child abuse were present in 20 cases (31%) on skeletal survey; only 35% of these were identified on bone scan. Six children (20%) had normal skeletal surveys, with abnormalities shown on bone scan. There were three children (10%) with normal bone scans who were shown to have injuries radiographically. CONCLUSIONS: Skeletal survey and bone scintigraphy are complementary studies in the evaluation of non-accidental injury, and should both be performed in cases of suspected child abuse.

Endovascular management of vein of Galen aneurysmal malformations presenting in the neonatal period.

BACKGROUND AND PURPOSE: Neonates with vein of Galen aneurysmal malformations (VGAMs) presenting with cardiac failure have high morbidity and mortality, and outcomes are significantly better in those presenting in later childhood. Neurologic outcomes in survivors are perceived to be uniformly poor, which may lead to the neonate being denied treatment. We assessed outcomes of modern neonatal intensive care and endovascular embolization in a consecutive series of such neonates presenting with cardiac failure. METHODS: Between 1996 and 1998, five infants (three male, two female) were diagnosed with symptomatic VGAMs in the first week of life, four of whom had intractable, high-output cardiac failure and underwent initial endovascular treatment. There were 15 endovascular procedures and one neurosurgical clipping in these five patients. Transarterial and transvenous routes were required, using multiple embolic agents. We emphasized the use of sonographically guided, percutaneous transtorcular-venous-access, moveable-core guidewire as an embolic agent; routine MR imaging; and MR angiography. RESULTS: Immediate outcomes included control of cardiac failure with normal neurologic function in four (80%) patients and one (20%) death from intractable cardiac failure. On follow-up examination, three (60%) infants showed no evidence of neurologic abnormality or cardiac failure; one (20%) infant showed moderate developmental delay. Two have had no further shunting on angiography, one has minimal flow, and one is awaiting follow-up imaging. CONCLUSION: Endovascular therapy with modern neuroanesthetic and neurointensive care can provide good outcomes even in the highest-risk neonates with VGAMs and cardiac failure. If medical management of cardiac failure fails, and there is no evidence of gross cerebral parenchymal damage on imaging, urgent endovascular treatment is feasible and can reduce the almost-100% mortality otherwise expected, without invariably severe morbidity. Use of multiple embolization strategies in multiple stages usually is necessary in these patients, and novel approaches and embolic agents may be necessary.

The DMSA scan in paediatric urinary tract infection.

The objective of the present paper was to review the use of the dimercaptosuccinic acid (DMSA) scan in urinary tract infection at British Columbia's Children's Hospital to determine the frequency of cortical defects and the association between vesico-ureteric reflux and the presence of cortical defects in children with urinary tract infection. A total of 129 consecutive children with a urinary tract infection referred for a DMSA scan in a 2-year period (January 1992-January 1994) were retrospectively studied. The results were analysed in terms of kidneys, and the incidence of cortical defects was determined. Eighty-eight patients (68%) had a radiographic micturating cysto-urethrogram within 6 months of the DMSA scan, and in this group the relationship of defects with vesico-ureteric reflux was determined. Overall, 81/258 (31%) of kidneys had a cortical defect on a DMSA scan. Of those who had a micturating cysto-urethrogram, 53/176 (30%) kidneys had vesico-ureteric reflux, and of those that had reflux, 21/53 (40%) had a cortical defect on a DMSA scan. In the group of children without reflux, 38/123 (31%) had a cortical defect. Renal cortical scan defects are common findings in paediatric urinary infection, and frequently occur in the absence of vesico-ureteric reflux. These defects represent either established scars or acute pyelonephritis that can proceed to scarring. The micturating cysto-urethrogram alone is insufficient as a screening modality to identify those kidneys at risk of renal scarring.

Correlation of MRI and CSF cytology in the diagnosis of medulloblastoma spinal metastases.

BACKGROUND: Medulloblastoma frequently spreads to involve the spinal cord, which significantly reduces patient survival and determines whether chemotherapy is utilised and the dose of irradiation to the neuraxis. Staging is usually achieved by MRI of the spine and/or cytology of CSF, both methods having their limitations. Objective. To determine whether there is a correlation between CSF cytology and the demonstration of spinal metastases by MRI and whether CSF cytology is useful when spinal MRI is equivocal. MATERIALS AND METHODS: All cases of medulloblastoma diagnosed at our hospital between 1992 and 1997 were identified. Of 26 cases, 11 presentations (age range 4 months to 12 years) had both CSF cytology (either from the cisterna magna or lumbar puncture) and spinal MRI. The MR studies were reviewed for the presence of metastases and the CSF cytology for the presence of tumour cells. RESULTS: We found 100% correlation between MRI and CSF cytology for samples taken by lumbar puncture (four negative and three positive on both investigations). No correlation was demonstrated when CSF samples were taken from the cisterna magna. Conclusions. Our data suggest that lumbar CSF cytology may be useful when the MRI is equivocal for the presence of metastatic involvement of the spine by medulloblastoma.

Intestinal rotational abnormalities in polysplenia and asplenia syndromes.

OBJECTIVE: To review the anomalies of intestinal rotation occurring in association with asplenia (right isomerism) and polysplenia (left isomerism) syndromes. MATERIALS AND METHODS: A retrospective study was performed of 27 children with asplenia (21) or polysplenia (6) identified from the cardiology and radiology databases from 1988 to 1996 and in whom an upper gastrointestinal barium study had been performed. The intestinal rotation was determined by reviewing the barium meal and could be divided into four groups: (1) normal rotation, (2) incomplete rotation or nonrotation, (3) reversed rotation and (4) reversed incomplete rotation or nonrotation. Surgical correlation was obtained at laparotomy in 17 patients. RESULTS: Of the 27 children studied, 3 (11 %) had normal rotation; incomplete rotation or nonrotation occurred in 5 (19 %), and 2 in this group developed midgut volvulus; 5 (19 %) had reversed rotation; 14 (52 %) had reversed incomplete rotation or nonrotation. CONCLUSION: Asplenia and polysplenia are frequently associated with intestinal malrotation, and a barium study is recommended in all of these children, as many will be at risk of midgut volvulus.

Wall enhancement of leaking polytetrafluoroethylene grafts: a new CT sign.

Perigraft seroma is a rare complication of synthetic vascular grafts. We describe a new sign observed in two children who underwent computed tomography of the chest for further evaluation of seromas complicating modified Blalock-Taussig procedures in which a polytetrafluoroethylene graft was used. In both patients contrast enhancement of the wall of the leaking graft was demonstrated on delayed imaging. One patient had bilateral grafts, and the enhancement was only demonstrated in the wall of the leaking graft. We discuss the possible mechanism of this finding and propose that this sign may be further evidence of abnormal graft permeability.

Sonographic measurement of renal enlargement in children with acute pyelonephritis and time needed for resolution: implications for renal growth assessment.

OBJECTIVE: Failure of a kidney to grow satisfactorily in childhood is evidence of renal disease. Because kidneys may enlarge during an episode of acute pyelonephritis, concomitant renal length measurements cannot be used as baselines for growth assessment. This study was designed to determine the degree of renal enlargement in children with acute pyelonephritis and the time the enlargement takes to resolve after treatment is started to find the optimum time for obtaining baseline measurements. SUBJECTS AND METHODS: In a cohort study, 180 children younger than 5 years old with their first proven acute urinary tract infection, with or without pyelonephritis, had renal scintigraphy and sonography within 15 days of starting treatment. The presence of cortical defects on scintigrams indicated pyelonephritis. The lengths of kidneys with and without scintigraphic defects (i.e., with and without pyelonephritis) were compared, adjusting for age and sex, and the length of kidneys with defects was related to time elapsed between the start of treatment and sonography. RESULTS: Ninety-nine kidneys (28%) in 77 children (43%) had scintigraphic defects. Kidneys with defects were an average of 3.2 mm longer than kidneys without defects. Length and time interval between treatment and sonography in kidneys with defects correlated negatively, with mean length approaching that of kidneys without defects by 10-11 days. CONCLUSION: Kidneys with acute pyelonephritis initially increase in length but return to normal on average by the 11th day of treatment. If poor renal growth is used as an indication of renal disease, sonography should be delayed or repeated at least 2 weeks after the start of treatment to determine the length of the uninflamed kidney.

Voiding cystourethrography in boys: does the presence of the catheter obscure the diagnosis of posterior urethral valves?

OBJECTIVE: In voiding cystourethrography, the urethral catheter may or may not be left in place during voiding. The main argument for removing the catheter is that the diagnosis of posterior urethral valves may be missed because the catheter can hold open the valve, efface it, and render it invisible. However, if the catheter does not prevent the diagnosis of urethral disease, it is preferable to leave it in place. The catheter makes it possible to repeat the procedure easily if necessary, and using it to drain the bladder provides information about ureteric obstruction in the presence of vesicoureteric reflux. Accordingly, the purpose of this study was to determine whether leaving the urethral catheter in place throughout voiding cystourethrography affects the efficacy of the procedure for the diagnosis of posterior urethral valves. MATERIALS AND METHODS: Three radiologists reviewed the preoperative voiding cystourethrograms obtained in 48 boys who ranged in age from 1 day to 10 years old (mean, 1.5 years). All patients had a diagnosis of posterior urethral valves made at cystoscopy, which was used as the gold standard. The voiding cystourethrogram was obtained with a catheter in place during voiding in 28 (58%) of the 48 boys, without a catheter in 17 (35%), and with and then without a urethral catheter during the voiding phase of the study in three (6%). RESULTS: Posterior urethral valves were detected on 25 (89%) of the 28 voiding cystourethrograms obtained with a urethral catheter in place and in 15 (88%) of the 17 voiding cystourethrograms done without a urethral catheter. The five children in whom posterior urethral valves had been diagnosed by cystoscopy but were not detected on voiding cystourethrography had no dilatation of the posterior urethra nor any other evidence of obstruction; these were possibly false-positive cystoscopic diagnoses. CONCLUSION: Our results show that a urethral catheter does not obscure posterior urethral valves in boys and need not be removed routinely during the voiding phase of voiding cystourethrography.

Wilms' tumor: a rational use of preoperative imaging.

OBJECTIVE: To determine whether a preoperative imaging protocol relying predominantly on a chest X-ray film (CXR) and ultrasound in patients with Wilms' tumor is adequate for patient management and to determine the frequency more sophisticated imaging, in particular, computed tomography (CT), is required. DESIGN AND SETTING: Historical cohort study at a tertiary pediatric hospital. SUBJECTS: 60 consecutive patients with Wilms' tumor treated at our institution between 1980 and 1990. MAIN OUTCOME MEASURE: The preoperative imaging was recorded and 2- and 4-year survival were compared with the National Wilms' Tumor Study. RESULTS: 100% of patients had a preoperative CXR, 95% abdominal ultrasound, 5% abdominal CT, 13% chest CT, 47% abdominal X-ray, 2% aortography, 5% cavography, and 35% intravenous urography. The overall 2- and 4-year survivals of 92% and 90%, respectively, did not statistically differ from the National Wilms' Tumor Study 2- and 4-year survivals of 94% and 91%. CONCLUSIONS: A preoperative imaging protocol relying predominantly on a CXR and abdominal ultrasound does not reduce survival. Other more sophisticated imaging, in particular, CT, is not required in the majority of cases and is warranted only when a CXR or ultrasound is unable to resolve relevant management problems.

Assessment of airways compression by MR imaging in children with aneurysmal pulmonary arteries.

Magnetic resonance imaging (MRI) has an established role in the accurate and non invasive assessment of airways compression by congenital vascular rings and pulmonary artery slings, making angiography of these lesions unnecessary. This role can be broadened to encompass other vascular compressive lesions, as in the two pediatric patients described here with aneurysmal pulmonary arteries of different etiology, one congenital and the other acquired.

Risk factors in the development of early renal cortical defects in children with urinary tract infection.

OBJECTIVE: Defects seen on early cortical scintigrams of the renal cortex in children with urinary tract infection may represent acute inflammatory change or established scar. The purpose of this study was to determine the relationship between these defects and age, sex, the presence and grade of vesicoureteral reflux, and infective organism in a cohort of children examined after their first proved urinary tract infection. SUBJECTS AND METHODS: We prospectively examined 193 consecutive patients less than 5 years old who were seen at the ambulatory pediatric department during a 3-year period and had a first proved urinary tract infection. Children with obstructed or solitary kidneys were excluded. All patients were imaged with scintigraphy of the renal cortex and radiographic voiding cystourethrography within 15 days of diagnosis. The association of age, sex, the presence and grade of vesicoureteral reflux, and infective organism with a defect (acute pyelonephritis or a renal scar) seen on a cortical renal scan was studied. RESULTS: The prevalence of cortical defects was greater in the kidneys of patients less than 2 years old (96/290, 33%) than in older children (16/96, 17%) and greater in those with vesicoureteral reflux (41/92, 45%) than in those without it (71/294, 24%). Vesicoureteral reflux was absent in 63% (71/112) of kidneys with a cortical defect. No association with sex or infective organism was established. As well as having a greater prevalence of cortical defects, 145 (75%) of the 193 urinary tract infections included in the study were in children less than 2 years old. The kidneys of these younger patients also had a greater severity and prevalence of vesicoureteral reflux (74/290, 26%) than did those of older children (18/96, 19%). CONCLUSION: Early cortical defects are associated with an age less than 2 years and vesicoureteral reflux. However, the association of early defects with the presence and grade of vesicoureteral reflux is confounded by the declining prevalence and severity of reflux with age. A significant proportion of cortical defects occur in the absence of vesicoureteral reflux, and the contribution of reflux to scar formation might be less than previously considered.

Vesicoureteral reflux: an accurate predictor of acute pyelonephritis in childhood urinary tract infection?

PURPOSE: To determine the association between vesicoureteral reflux (VUR) and the presence of acute pyelonephritis in children with urinary tract infections. MATERIALS AND METHODS: The authors studied 150 consecutive patients less than 5 years of age with their first proved urinary tract infection. All patients underwent renal cortical scintigraphy (with technetium-99m dimercaptosuccinic acid or Tc-99m gluconate) and voiding cystourethrography (VCUG) to identify the presence of cortical defects and VUR, respectively. RESULTS: Of 300 kidneys, 88 (29.3%) had a cortical defect at scintigraphy. Fifty-four of the 88 patients (61%) did not have VUR demonstrated at VCUG. Conversely, 72 of the 300 kidneys (24%) had VUR; of these, 38 (53%) had no cortical defect. The sensitivity of VCUG in helping predict a defect was 38.6%, and the specificity was 82.1%. CONCLUSION: VUR (as shown by VCUG) and renal cortical scintigraphic defects frequently occur independently of each other. Renal cortical scintigraphy may be a more accurate predictor of patients at risk for scarring.

Is the preliminary film necessary prior to the micturating cystourethrogram in children?

The aim of the study was to determine the value of the preliminary film in children undergoing a micturating cystourethrogram (MCU). The coded computer reports of 806 children undergoing MCUs in a 12-month period were retrospectively reviewed for abnormalities of the lumbar spine, hips, or for calcifications. Vesicoureteric reflux was present in 185 patients (23%). Four patients had renal calculi (0.5%), and in all cases the abnormality was evident on preceding imaging of the upper urinary tract. Spinal anomalies (other than known meningomyelocele) were present in four patients. The clinically obvious abnormalities present in these were a sacral teratoma, a sacral lipoma, scoliosis with tracheo-oesophageal fistula, and a cutaneous angioma with a sacral pit. No patients (other than those with known meningomyelocele) had dislocated hips diagnosed. If the preliminary film had not been performed in 806 patients, neither spinal anomaly, renal calculus, nor congenital dislocated hip would have been missed. The low incidence of plain film anomalies indicates that in our population a plain film is not justified routinely.

Liver CT: a practical approach to dynamic contrast enhancement.

The aim of this study was to establish a practical, simple protocol that reliably produces high quality dynamic incremental computed tomography (CT) of the liver. We reviewed 90 patients randomly allocated into six different protocols. All had preliminary unenhanced scans followed by a dynamic incremental CT of the liver. An initial delay of 30 seconds was used from the commencement of the injection of Iopamiro 370. The groups were: 1. Pump infusion (a) 100 mls at 2 mls/sec scanning inferosuperiorly. (b) 100 mls at 2 mls/sec scanning superoinferiorly. (c) 100 mls at 1 ml/sec scanning inferosuperiorly. (d) 50 mls at 1 ml/sec scanning inferosuperiorly. 2. 40 mls hand injected bolus followed immediately by 60 ml pump infusion at 1.3 mls/sec scanning inferosuperiorly. 3. 50 mls hand injected bolus scanning inferosuperiorly. The parameters recorded were the degree of hepatic parenchymal and hepatic venous enhancement and the aortic--IVC difference at the last slice through the liver, all measured in Hounsfield units. The protocols using 100 mls of contrast produced approximately twice the parenchymal and hepatic venous enhancement compared with those using 50 mls. Approximately 60-90% of examinations using 100 mls produced scans through the entire liver during the bolus or nonequilibrium phase, deemed the most sensitive for the detection of focal lesions, compared with 13-33% of those using 50 mls. Equally satisfactory results were obtained using the relatively inexpensive Biotel power injector preceded by a 40 ml hand injected bolus, compared with using an Angiomat angiography infusion pump.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of duplex Doppler sonography of the ligamentum teres and portal vein with endoscopic demonstration of gastroesophageal varices in patients with chronic liver disease or portal hypertension, or both.

The ability of duplex Doppler sonography of the ligamentum teres and portal vein to detect specific signs of portal hypertension was compared with the ability of endoscopy to demonstrate gastroesophageal varices in consecutive patients. Among 90 patients with parenchymal liver disease and a high probability of portal hypertension, 70 had varices, 72 had specific sonographic signs, and four had neither. Ultrasonography was comparable to endoscopy irrespective of the clinical severity of the underlying liver disease. Eleven patients had vascular occlusive diseases; nine had varices; and all had at least one sonographic sign. Duplex Doppler ultrasonography may have a clinical role in noninvasive detection of portal hypertension. Further studies correlating the findings with those of portal pressure are needed to define the place of duplex Doppler ultrasonography as a predictor of the presence of portal hypertension.