Incidental Findings on Pediatric Abdominal Magnetic Resonance Angiography

Rationale and Objectives

Abdominal magnetic resonance angiography (MRA) has gained favor in pediatric patients owing to its lack of ionizing radiation and noninvasive nature. Reports exist regarding incidental findings on body MRA in adult patients. However, the incidental findings in pediatric abdominal MRA have not been previously reported. Our study aims to determine the frequencies, characteristics, and categories of incidental findings in pediatric patients undergoing abdominal MRA.

Materials and Methods

Retrospective study was performed in 78 consecutive contrast-enhanced abdominal MRA of patients between ages 0 and 20 years over a 7-year time period. The presence of incidental vascular and extravascular findings was noted. Reports were categorized in consensus by two radiologists as no incidental finding (group A), normal or normal variants or nonsignificant incidental common findings (group B), or abnormal incidental findings (group C). Group C was reviewed to determine whether additional management was performed.

Results

A total of 40 boys and 38 girls (51%:49%) were reported, with a mean age of 12.3 years (standard deviation ±5.6 years, range 7 days to 20 years). Three most common indications for MRA were renal artery stenosis (24.4%), vasculitis (21.8%), and suspected intra-abdominal venous thrombosis (14.1%). We identified a total of 92 incidental findings in 50 of 78 patients; 60 findings in 29 patients in group B, and 32 findings in 21 patients in group C. Atelectasis at the lung bases was the most common incidental finding in group B (14 of 78 patients). The most common findings in group C were ascites, scoliosis, and splenomegaly. There were three abnormal incidental findings that led to causative workup and/or further management (moderate ascites, pericardial and pleural effusion, and venous malformation). The remaining cases with abnormal findings received treatment of their primary conditions only.

Conclusions

Pediatric abdominal MRA revealed a large number of incidental findings. The large majority were findings without clinical significance. Basal lung atelectasis was the most common overall incidental and nonsignificant finding, whereas ascites was the most common abnormal incidental finding. Although not all abnormal incidental findings affected management, appropriate identification and communication of relevant findings would improve patient care.

Introduction

Magnetic resonance angiography (MRA) is a noninvasive method for evaluation of arterial blood vessels . It has many advantages such as excellent tissue contrast, multi-planar imaging capability, and non-contrast angiographic imaging. Recently, MRA has become the favored mode of angiographic imaging over computed tomography angiography or digital subtraction angiography in pediatric patients owing to its lack of ionizing radiation and noninvasive nature .

The preference for MRA in pediatric patients also holds true with respect to imaging of abdominal vasculature. Common indications for abdominal MRA of children are renal artery stenosis, vasculitis, tumor vascularity, portal hypertension, and transplant evaluation . There is no single widely accepted standard protocol of abdominal MRA in children. Additionally, there is variability in the amount of non-angiographic sequences performed to assess extravascular structures.

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Materials and Methods

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TABLE 1

Current Institutional Protocol for Pediatric MRA

Sequences Plane TR/TE (ms) Flip Angle NSA Slice Thickness/Spacing (mm) Rationale T2-weighted single-shot fast spin echo Coronal 1065/865 142 2 4/−2 Overview anatomic assessment T2-weighted motion correction radial fat-saturated sequence Axial 6375/93.6 142 2 4/0 General anatomic assessment, motion-resistant sequence useful in pediatric patients T1-weighted SPGR DIXON fat saturated (including in/opposed phase) Axial 7.4/1.9 10 0.7 3.2/−1.6 Anatomic assessment, characterization of the lesion before contrast-enhanced phase Time resolved MRA sequence Coronal 3.4/1.4 16 0.75 3/−1.5 High temporal and spatial volumetric MRA imaging T1-weighted SPGR DIXON fat saturated (including in/opposed phase) Axial and coronal 7.4/1.9 10 0.7 3.2/−1.6 Delayed imaging

MRA, magnetic resonance angiography; NSA, number of signal averages; SPGR, spoiled gradient recalled echo; TR/TE, repetition time/echo time.

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Results

Demographic Data

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TABLE 2

Indications for MRA

Conditions Number of Cases (%) Renal artery stenosis 19 (24.4%) Vasculitis 17 (21.8%) Suspected intra-abdominal venous thrombosis 11 (14.1%) Vascular malformation, aneurysm, syndromic abnormality 11 (14.1%) Post liver transplantation concerning for vascular complication 7 (9.0%) Other venous conditions such as venous shunt, portal hypertension with shunt, Budd-Chiari syndrome 6 (7.7%) Preoperative evaluation of neuroblastoma or retroperitoneal mass 3 (3.8%) Others such as abdominal pain, nausea, vomiting 3 (3.8%) No given history 1 (1.3%)

MRA, magnetic resonance angiography.

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Incidental Findings on MRA

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TABLE 3

Incidental Findings Deemed Clinically Insignificant (“Group B”)

System, Organ Findings Total (%) Reproductive tract Small ovarian cyst (1) 1 (1.7%) Urinary tract Extrarenal pelvises (2), renal cysts (2), atrophic kidney (1), absent unilateral kidney (1), unilateral hypertrophy (1) 7 (11.7%) Lymph nodes Enlarged LN > 1 cm in short axis (3) 3 (5.0%) Visualized basal lungs and mediastinum Atelectasis (14), trace pleural effusion (3), trace pericardial effusion (3) 20 (33.3%) Hepatobiliary system Mild IHD dilatation (1), small hemangioma (1), hepatic cyst (1), bile sludge (1), variant left hepatic lobe (1) 5 (8.3%) Bowel Dilated loops (2) 2 (3.3%) Spleen and pancreas Pancreatic divisum (2), accessory spleen (1) 3 (5.0%) Musculoskeletal system Dependent edema (2), pectus excavatum (1), bilateral 13th ribs (1) 4 (6.7%) Incidental vascular findings Accessory renal artery (6), retroaortic left renal vein (2), circumaortic left renal vein (1), common origin of celiac axis and SMA (1), replaced right hepatic artery (1) 11 (18.3%) Others Minimal physiologic fluid in pelvic cavity (3), situs inversus (1) 4 (6.7%) Total 60 (100%)

IHD, intrahepatic duct; LN, lymph node; SMA, superior mesenteric artery.

TABLE 4

Incidental Findings Deemed Clinically Significant (“Group C”)

System, Organ Findings Total (%) Reproductive tract Hemorrhagic cyst (1) 1 (3.1%) Urinary tract Angiomyolipoma (1), atrophic kidney with scar (1) 2 (6.3%) Visualized basal lungs and mediastinum Moderate pleural effusion (1), large pericardial effusion (1), pneumonia (1) 3 (9.4%) Hepatobiliary system Hepatomegaly (1), hepatic steatosis (1), isolated CHD dilatation (1), gallstone (1) 4 (12.5%) Spleen and pancreas Splenomegaly (4), pancreatitis (1) 5 (15.6%) Musculoskeletal system Scoliosis (4), anterior compression fracture with degenerative disc and end plate (1), peripheral nerve sheath tumor or myxoid tumor (1) 6 (18.8%) Neurologic system Neurofibroma (1; Fig 4 ) 1 (3.1%) Incidental vascular findings Nutcracker syndrome (1; Fig 5 ), venous malformation (1), significant dilated superficial and deep vein of pelvis (1) 3 (9.4%) Others Ascites (6), umbilical hernia (1) 7 (21.8%) Total 32 (100%)

CHD, common hepatic duct.

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Further Management of Abnormal Incidental Findings

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TABLE 5

Recorded Follow-up of Clinically Significant Incidental Findings (“Group C”) Listed By Organ System

System Abnormal Incidental Findings (Group C) Further Workup or Management Musculoskeletal system A peripheral nerve sheath tumor or myxoid tumor Advised and followed up with ultrasound, not surgery Musculoskeletal system Mild to moderate S-shaped scoliosis Periodic X-ray and follow-up with orthopedist Incidental vascular findings Venous malformation at right renal hilum and dilated superficial and deep vein in pelvis Further dedicated MRI of the abdomen and pelvis Others Moderate amount of ascites Worked up and treated protein-losing enteropathy and multiple food allergies with enteritis (no definite diagnosis and patient was lost to follow-up), no record of abdominal paracentesis Others Moderate left and small right pleural effusion, large pericardial effusion, small amount of ascites, hepatomegaly, and splenomegaly Worked up and treated SLE with LN, no record of pleural or pericardial drainage

LN, Lupus nephritis; MRI, magnetic resonance imaging; SLE, systemic lupus erythematosus.

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Discussion

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Appendix

Supplementary Data

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Table S1

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