endorectal ultrasound

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Related to endorectal ultrasound: Transrectal ultrasound

Endorectal Ultrasound



Endorectal ultrasound (ERUS) is a procedure where a probe is inserted into the rectum and high frequency sound waves (ultrasound waves) are generated. The pattern of echoes as they bounce off tissues is converted into a picture (sonogram) on a television screen.


ERUS is used as a diagnostic procedure in rectal cancer to determine stage of the tumor and as a post-radiation, presurgical examination to assess extent of tumor shrinkage. ERUS can also be used in cases of anal fistula (an abnormal passage) and problems with the anal sphincter muscles (muscles that control the opening and closing of the anus).


Normal precautions should be taken with any diagnostic procedure. Since the population in which this procedure is normally done is elderly, the imaging staff should be extra cautious about stressing the patient. The procedure is invasive and may be embarrassing to some. Other patients may be anxious about their medical condition since endorectal ultrasounds are not routine. This places an added burden on already stressed hearts and nervous systems. Physicians, nurses, and technicians may need to be prepared for stress reactions that could include the heart, asthma, or anxious behaviors.


ERUS has been used as a means to determine the depth of rectal cancers and to assess whether the tumor has affected surrounding tissues. This pre-treatment procedure has proven to be an accurate tool for tailoring surgery for patients.
Problems with interpretation of the sonograms after radiation and before surgery have resulted in tumors being identified that were merely the formation of fibrous tissues that remained after the tumors had been eliminated by the radiation. Yet, some of the fibrous areas actually hid residual tumors. Rectal anatomy itself can affect the accuracy of ultrasound reading. This makes ERUS problematic in determining the amount of tumor reduction a patient has after radiation therapy.


The patient must evacuate the bowels completely before the procedure is done. This usually is assisted though the use of several enemas. The patient may be told to adhere to a liquid diet the day prior to doing this procedure. The probe is inserted, usually with little discomfort for the patient since it will only be examining the first few inches of the colon.


Since ERUS is a minor invasive procedure, there is no aftercare.


There are no risks to having an ultrasound.

Normal results

Normal results after an endorectal ultrasound are normal, healthy tissues.

Abnormal results

Abnormal results range from any number of congenital deformities in the lining of the rectum to serious rectal cancers.



Johnston, Lorraine. Colon and Rectal Cancer: A Comprehensive Guide for Patients and Families. Sebastopol, CA: O'Reilly, 2000.
Levin, Bernard. Colorectal Cancer: A Thorough and Compassionate Resource for Patients and Their Families. New York: Villard, 1999.


Gavioli, M. A. Bagni, I. Piccagli, S. Fundaro, and G. Natalini. "Usefulness of Endorectal Ultrasound after Preoperative Radiotherapy in Rectal Cancer: Comparison between Sonographic and Histopathologic Changes." Dis ColonRectum (August 2000): 1075-83.


American Society of Colon and Rectal Surgeons."Practice Parameters for the Treatment of Rectal Carcinoma." May 9, 2001. 〈http://www.asco.org/prof/me/html/abstracts/gasc/m_969.htm〉.
National Cancer Institute. "NCI/PDQ Patient Statement:Rectal Cancer Updated 11/2000." OncoLink. May 9, 2001. 〈http://www.oncolink.upenn.edu/pdq_html/2/engl/200076.html〉.

Key terms

Anal sphincter muscles — Muscles that control the opening and closing of the anus.
Fistula — An abnormal passage.
Sonogram — The picture formed by the pattern of echoes from an ultra sound.
Ultrasound waves — High frequency sound waves.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

endorectal ultrasound

Abbreviation: ERUS
1. An imaging technique in which an ultrasound transducer is placed inside the rectum and used to evaluate the depth of colon and prostate cancers and the extent to which they have spread to neighboring lymph nodes.
2. Transrectal ultrasound.
See also: ultrasound
Medical Dictionary, © 2009 Farlex and Partners
References in periodicals archive ?
* The recommended use of endorectal ultrasound or MRI in the initial work-up and staging of patients with rectal cancer, particularly in patients with early lesions.