Intravenous blood pool activity masquerading as gastrointestinal hemorrhage

Abstract

Radiolabeled red blood cell (RBC) scintigraphy is a common study to detect and localize gastrointestinal hemorrhage. There are many potential entities that may result in false-positive RBC scintigraphy. Here, we present a case of enlarged feeding vessels of omental carcinomatosis which scintigraphically might be mistaken as intraluminal bowel activity and thus active hemorrhage. This case highlights the importance of reviewing correlative imaging in patients with a large neoplastic burden.

Keywords

Altered blood pool anatomy - false-positive bleed - omental carcinomatosis - red blood cell scintigraphy

Introduction

Effective therapy for acute gastrointestinal (GI) bleed requires precise localization of the hemorrhage site. Red blood cell (RBC)-labeled scintigraphy is a common imaging modality for detecting the location of a lower GI bleed. Its increased sensitivity for low flow bleeds compared to fluoroscopic and computed tomography (CT) angiography (CTA) make it an important part of the lower GI bleed treatment algorithm. This report describes a vascular abnormality secondary to omental carcinomatosis, which could lead to a false-positive interpretation if not corroborated with other anatomic imaging.

Case Report

A 71-year-old male with biopsy-proven metastatic renal cell carcinoma and current warfarin therapy for recurrent pulmonary embolism was admitted to the intensive care unit after presenting with suspected intra-abdominal blood loss. CTA was performed but failed to show a definitive source of hemorrhage; however, complex peritoneal fluid was identified and appeared denser near the prior partial nephrectomy site. Endoscopy was not performed. After intravenous administration of 1.017 GBq (27.5 mCi) of99m Tc-radiolabeled autologous erythrocytes, the patient underwent dynamic anterior planar imaging for 90 min. RBC scintigraphy demonstrated serpiginous areas of increased activity which did not move or change in intensity [Figure 1a]. Comparison with three-dimensional rendering of CTA acquired earlier showed enlarged gastroepiploic and splenic arteries supplying omental carcinomatosis [Figure 1b] corresponding to abnormal activity seen on scintigraphy. Recent ¹⁸F-fluorodeoxyglucose-positron emission tomography/CT demonstrated a large metastatic burden, particularly to the omentum [Figure 1c] and [Figure 1d].

Figure 1 Anterior static scintigraphic image of ^99mTc-radiolabeled autologous erythrocytes (a), along with a color-labeled three-dimensional reconstruction of the patient´s recent computed tomography angiography of the abdomen and pelvis. Serpiginous-shaped activity on scintigraphy (b)corresponds to the enlarged gastroepiploic (arrows) and splenic (arrowheads) arteries supplying the omental carcinomatosis (asterisks). A single-slice coronal ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography fusion image (c) and the maximal intensity projection from the same study (d) highlight the fluorodeoxyglucose avid metastatic burden in the left lower quadrant (asterisks)

Discussion

The serpiginous activity on scintigraphy could be misconstrued for intraluminal activity and hemorrhage, although the activity failed to move or change in intensity. Scintigraphic criteria for active GI bleeding include radiotracer outside expected blood pool structures, increasing intensity over time, and anterograde or retrograde movement conforming to the bowel.[1],[2],[3] However, movement consistent with bowel would not be required for diagnosing peritoneal or retroperitoneal hemorrhage.[4],[5],[6] In this case, the patient's prior CTA demonstrated that the cause of the abnormal scintigraphic findings was due to enlarged feeding vessels of the omental carcinomatosis.

Other potential entities that have been reported to cause false-positive RBC scintigraphy include varices, hematomas, aneurysms, and hemangiomas.[7],[8],[9],[10] If no correlative imaging is available, single-photon emission computed tomography (SPECT)/CT could be performed to aid in defining the abnormal distribution and confirm the findings. Unfortunately, the patient was unable to undergo SPECT/CT due to his critical condition.

This case highlights the importance of reviewing correlative imaging prior to scintigraphy in patients with large neoplastic burdens where blood pool anatomy can be significantly altered. In our patient, we were able to anticipate how the abnormal vasculature and large masses might alter the scintigraphic appearance. It is recommended to review recent CT and magnetic resonance imaging beforehand to understand the patient's anatomy and any abnormal variants or pathology which might hinder correct interpretation of the study.[1]

Conflict of Interest

There are no conflicts of interest.

Financial support and sponsorship

Nil.

• References

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Publication History

Received: 01 April 2019

Accepted: 18 July 2019

Article published online:
19 April 2022