Rectal gas volume: Defining cut-offs for screening for evacuation disorders in patients with constipation

S. Y. Park, D. Khemani, Andres Acosta, D. Eckert, Michael Camilleri

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Background: Diagnosis of rectal evacuation disorders (RED) is currently based on anorectal manometry (ARM) and evacuation tests in specialized laboratories; we recently showed higher rectal gas volume (RGV) and maximum rectal gas transaxial area (MRGTA) measured on abdominal and pelvic computed tomography (CT) in patients with documented RED.The aim of this study was to obtain cut-off values of RGV, MRGTA, and rectal area on scout film (RASF) to differentiate constipated patients with RED from those without RED, based on ARM, balloon expulsion test (BET), and colon transit test. Methods: We identified 118 constipated patients (65 with RED) with prior record of CT. Using standard CT software, we used a variable region of interest (ROI) program to measure RGV, MRTGA, and RASF, as previously described. We constructed receiver operating characteristics curves based on different values, and we estimated AUC, specificity, and positive predictive value (PPV) to detect RED in patients with constipation. Key Results: Receiver operating characteristics of the models to predict RED showed AUC 0.751 for RGV and 0.737 for MRGTA (both P<.001), and 0.623 for RASF (P=.029). At specificity of 90%, RGV of 30 mL had a PPV 77.3%, MRGTA of 10 cm2 had a PPV 75.0%, and RFAS of 9 cm2 had a PPV of 68.8% for identifying constipated patients with RED. Conclusions & Inferences: Rectal gas measurements on abdominal imaging may indicate RED in patients with constipation. At ~90% specificity for RED, RGV of 20 or 30 mL or MRGTA of 10 cm2 on CT has PPV ~75%, and RASF of >9 cm2 has PPV of ~69%.

Original languageEnglish (US)
JournalNeurogastroenterology and Motility
DOIs
StateAccepted/In press - 2017

Fingerprint

Rectal Diseases
Constipation
Gases
Tomography
Manometry
ROC Curve
Area Under Curve
Colon
Software

Keywords

  • Area
  • Colonic transit
  • Radiograph
  • Specificity

ASJC Scopus subject areas

  • Physiology
  • Endocrine and Autonomic Systems
  • Gastroenterology

Cite this

@article{572201d3b13a455eb26743b9b377ffbe,
title = "Rectal gas volume: Defining cut-offs for screening for evacuation disorders in patients with constipation",
abstract = "Background: Diagnosis of rectal evacuation disorders (RED) is currently based on anorectal manometry (ARM) and evacuation tests in specialized laboratories; we recently showed higher rectal gas volume (RGV) and maximum rectal gas transaxial area (MRGTA) measured on abdominal and pelvic computed tomography (CT) in patients with documented RED.The aim of this study was to obtain cut-off values of RGV, MRGTA, and rectal area on scout film (RASF) to differentiate constipated patients with RED from those without RED, based on ARM, balloon expulsion test (BET), and colon transit test. Methods: We identified 118 constipated patients (65 with RED) with prior record of CT. Using standard CT software, we used a variable region of interest (ROI) program to measure RGV, MRTGA, and RASF, as previously described. We constructed receiver operating characteristics curves based on different values, and we estimated AUC, specificity, and positive predictive value (PPV) to detect RED in patients with constipation. Key Results: Receiver operating characteristics of the models to predict RED showed AUC 0.751 for RGV and 0.737 for MRGTA (both P<.001), and 0.623 for RASF (P=.029). At specificity of 90{\%}, RGV of 30 mL had a PPV 77.3{\%}, MRGTA of 10 cm2 had a PPV 75.0{\%}, and RFAS of 9 cm2 had a PPV of 68.8{\%} for identifying constipated patients with RED. Conclusions & Inferences: Rectal gas measurements on abdominal imaging may indicate RED in patients with constipation. At ~90{\%} specificity for RED, RGV of 20 or 30 mL or MRGTA of 10 cm2 on CT has PPV ~75{\%}, and RASF of >9 cm2 has PPV of ~69{\%}.",
keywords = "Area, Colonic transit, Radiograph, Specificity",
author = "Park, {S. Y.} and D. Khemani and Andres Acosta and D. Eckert and Michael Camilleri",
year = "2017",
doi = "10.1111/nmo.13044",
language = "English (US)",
journal = "Neurogastroenterology and Motility",
issn = "1350-1925",
publisher = "Wiley-Blackwell",

}

TY - JOUR

T1 - Rectal gas volume

T2 - Defining cut-offs for screening for evacuation disorders in patients with constipation

AU - Park, S. Y.

AU - Khemani, D.

AU - Acosta, Andres

AU - Eckert, D.

AU - Camilleri, Michael

PY - 2017

Y1 - 2017

N2 - Background: Diagnosis of rectal evacuation disorders (RED) is currently based on anorectal manometry (ARM) and evacuation tests in specialized laboratories; we recently showed higher rectal gas volume (RGV) and maximum rectal gas transaxial area (MRGTA) measured on abdominal and pelvic computed tomography (CT) in patients with documented RED.The aim of this study was to obtain cut-off values of RGV, MRGTA, and rectal area on scout film (RASF) to differentiate constipated patients with RED from those without RED, based on ARM, balloon expulsion test (BET), and colon transit test. Methods: We identified 118 constipated patients (65 with RED) with prior record of CT. Using standard CT software, we used a variable region of interest (ROI) program to measure RGV, MRTGA, and RASF, as previously described. We constructed receiver operating characteristics curves based on different values, and we estimated AUC, specificity, and positive predictive value (PPV) to detect RED in patients with constipation. Key Results: Receiver operating characteristics of the models to predict RED showed AUC 0.751 for RGV and 0.737 for MRGTA (both P<.001), and 0.623 for RASF (P=.029). At specificity of 90%, RGV of 30 mL had a PPV 77.3%, MRGTA of 10 cm2 had a PPV 75.0%, and RFAS of 9 cm2 had a PPV of 68.8% for identifying constipated patients with RED. Conclusions & Inferences: Rectal gas measurements on abdominal imaging may indicate RED in patients with constipation. At ~90% specificity for RED, RGV of 20 or 30 mL or MRGTA of 10 cm2 on CT has PPV ~75%, and RASF of >9 cm2 has PPV of ~69%.

AB - Background: Diagnosis of rectal evacuation disorders (RED) is currently based on anorectal manometry (ARM) and evacuation tests in specialized laboratories; we recently showed higher rectal gas volume (RGV) and maximum rectal gas transaxial area (MRGTA) measured on abdominal and pelvic computed tomography (CT) in patients with documented RED.The aim of this study was to obtain cut-off values of RGV, MRGTA, and rectal area on scout film (RASF) to differentiate constipated patients with RED from those without RED, based on ARM, balloon expulsion test (BET), and colon transit test. Methods: We identified 118 constipated patients (65 with RED) with prior record of CT. Using standard CT software, we used a variable region of interest (ROI) program to measure RGV, MRTGA, and RASF, as previously described. We constructed receiver operating characteristics curves based on different values, and we estimated AUC, specificity, and positive predictive value (PPV) to detect RED in patients with constipation. Key Results: Receiver operating characteristics of the models to predict RED showed AUC 0.751 for RGV and 0.737 for MRGTA (both P<.001), and 0.623 for RASF (P=.029). At specificity of 90%, RGV of 30 mL had a PPV 77.3%, MRGTA of 10 cm2 had a PPV 75.0%, and RFAS of 9 cm2 had a PPV of 68.8% for identifying constipated patients with RED. Conclusions & Inferences: Rectal gas measurements on abdominal imaging may indicate RED in patients with constipation. At ~90% specificity for RED, RGV of 20 or 30 mL or MRGTA of 10 cm2 on CT has PPV ~75%, and RASF of >9 cm2 has PPV of ~69%.

KW - Area

KW - Colonic transit

KW - Radiograph

KW - Specificity

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U2 - 10.1111/nmo.13044

DO - 10.1111/nmo.13044

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SN - 1350-1925

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