COLONIC RESERVOIR EVALUATION BY SCINTIGRAPHY WITH [Tc-99m] COLLOID

ABSTRACT

In order to evaluate the intestinal emptying of patients submitted to direct anastomosis compared to those with colonic pouches, 28 patients (pts) (16 females and 12 males; ages ranging from 30-78 years, mean 53.2 years) submitted to partial rectocolectomy, were studied. Twelve pts had straight coloanal anastomosis and 16 had colonic pouches. An artificial material (a mixture of distilled water, psyllium mucilloid suspension and [Tc-99m] microcolloid) with a consistency resembling feces was introduced into the anus until the patient felt the sensation of evacuation. Static images in the left lateral and posterior projections of the abdomen with 100,000 counts were then acquired. After evacuation, a new set of static images was acquired for the same time of the pre-evacuation images. Regions of interest were drawn and the percentages of emptying were calculated. The mean percentage of emptying was 51.4% for the pts with straight coloanal anastomosis and 89.9% for the pts with colonic pouch. These results showed an excellent correlation between the symptoms and the type of intestinal transit reconstruction. Colonic reservoir scintigraphy is a promising method for the evaluation of the emptying ability of these reservoirs.

INTRODUCTION

Intestinal transit reconstruction by straight coloanal anastomosis has been widely used after resection of the rectum. Despite maintenance of sphincteric function, many patients complain of evacuation urgency, fragmented feces and some degree of incontinence. With the advent of J-pouch colonic reservoirs, these symptoms seem less frequent.

The J-pouch colonic reservoir technique, created by Parc et al. (1) and Lazorthes et al. (2) in 1986, for restoration of intestinal transit, emerged from the successful results of the ileal reservoir surgeries. This technique has resulted in less frequent bowel movements, as well as a smaller incidence of fragmented evacuations and urgency because of the higher reservoir capacity (3-6). Nevertheless, some patients show post-operative constipation that could be due to a longer reservoir loop or to a paradoxical puborectal contraction (7). Therefore this technique still requires further studies to achieve the ideal functional outcome for these patients.

The conventional radiological methods (pouchography and barium enema) used to evaluate the emptying of the intestinal content are difficult to perform and to interpret, because of the necessity of complex mathematical calculations and are influenced by patient positioning. The scintigram is easier to perform, is not significantly influenced by patient positioning and can quantify precisely the percentage of emptying after evacuation. It is physiological and results in a low patient dosimetry. There are only a few reports in the literature using scintigraphy, but without a rigid standardization of the methology.

The aims of this study are to suggest a standardization of the scintigraphic methodology to be used in the evaluation of the emptying of colonic pouches and to compare the intestinal emptying after evacuation in patients submitted to straight coloanal anastomosis (SCAA) and in those with J-pouch colonic reservoirs (JPCR).

MATERIALS AND METHODS

Twenty eight patients (12 male and 16 female; ages 30 to 78 years mean 53.2 years) submitted to partial rectocolectomy were studied. The reconstruction of intestinal transit was obtained by straight coloanal anastomosis (SCAA) (12 patients) or by a J-pouch colonic reservoir (JPCR)(16 patients). In both groups the protective stomas had been closed for at least 1 year.

METHODS

The bowel was prepared prior to the examination, by introducing into the anus a phosphate enema (Enemaplex^TM, Fresenius Laboratories, Campinas, Brazil, with 16 g of monosodium phosphate.H₂0, 6 g of disodium phosphate.7H₂0 and 100 ml of water resulting in a total volume of 130 ml), 30 minutes prior to image acquisition.

The radioactive artificial stool was prepared with a consistency similar to feces (7.2 g of mucilloid suspension of psyllium [Metamucil^TM] mixed with 300 ml of distilled water, at room temperature) and 111 MBq of ^99mTc-microcolloid was added to the artificial stool. The patients were placed in the left lateral position and the artificial stools were instilled into the anus by catheterization with a maximum speed of 13 ml/min either until the patients referred the need to evacuate or a maximum volume of 200 ml had been instilled.

Before evacuation static images with 100,000 counts each of the colon (in the SCAA group) or of the reservoir (in the JPCR group) were obtained in the lateral projection of abdomen and pelvis, with the patients in the left lateral position. The time elapsed to acquire the 100,000 counts image was recorded.

The patients were then asked to stand in the upright position for 15 minutes and another 100,000 counts image in the antero-posterior projection of abdomen and pelvis was obtained. The time elapsed to acquire this image was also registered.

The patients were allowed to evacuate. After evacuation static images of the colon (in the SCAA group) (Figure 2) or of the reservoir (in the JPCR group)(Figure1) were obtained in the same positions (upright and left lateral) with the same time of acquisition used for the images obtained before evacuation.

Figure 1 (click=zoom)

Figure 2 (click=zoom)

Regions of interest were drawn over the colon or the reservoir in both the pre- and post-evacuation images in the posterior projection with the patient standing for a better visualization of the radioactive feces.

The emptying and retention percentages of the intestinal contents were calculated as follows:

% emptying = post-evacuation counts x 100 / pre-evacuation counts

% retention = 100 - % emptying

The patients were also submitted to a clinical evaluation and had their evacuatory function scored according to the following parameters: degree of continence, number of evacuations/day, need to use diapers, degree of feces fragmentation, feces consistency ( liquid to solid ), pain or bleeding on evacuation.

Each item was scored from 1 to 5 ( very poor, poor, regular, good and excellent ) and the clinical status of each patient was the mean of these scores.

RESULTS

There was good correlation between the emptying rate and the clinical status of the patients. The mean emptying rate of the SCAA group (n=12) was 51% +/- 27.98%, and for the JPCR group (n=16), 84.42% +/- 14.67%. (Figure 3 and 4) The statistical analysis using the Mann-Whitney non-parametric test demonstrated that the mean emptying rate of the JPCR group was significantly higher than the mean emptying rate of the SCAA group (p=0.003).

Figure 3 (click=zoom)

Figure 4 (click=zoom)

The mean clinical score was 2.2 in the SCAA group and 4.1 in the JPCR group. ( Table 2).

DISCUSSION

The reconstruction of the intestinal transit by straight coloanal anastomosis has been widely performed to preserve the evacuatory function of patients submitted to rectal resection due to malignant or benign diseases (hemangiomas, radiation retitis). Although the sphincteric function is preserved, many patients complain of evacuatory urgency, fragmented feces and a variable degree of incontinence, mainly during the first two years after the surgery of transit reconstruction with reservoir.

With the advent of the colonic pouches, these complaints seem to be much less frequent and may be due to a better emptying of these pouches (3-6). It is known that the ileal reservoir with better emptying correlates with better continence, less frequent bowel movements and a smaller incidence of pouchitis.

The study of the intestinal emptying of the patients using scintigraphy is easy to perform and very precise. The dosimetry to the patient is minimal, with no risks. A few patients, however, would not be candidates to a scintigraphic study, such as patients with moderate fecal incontinence because of the risk of contamination of the field of view and inaccurate results. Locomotion incapacity or severe anal stenosis also led to difficulty in performing the study.

Some simple precautions should be taken. Artificial feces with higher concentration were studied but resulted in material too dense to be used. After the addition of psyllium to water with a spatula, the homogenization should be immediately done to avoid a precipitate formation. A more vigorous agitation (e.g. with an electric homogenizer) may result in a dense gel formation not amenable to instillation.

The instillation speed of the material can not be too high because these patients have low compliance and do not stand an abrupt colon or reservoir distention. Using an enema bag it is possible to make the artificial feces flow by gravity. The pear shape of the rectal catheter allows positioning just above the sphincters, resulting in satisfactory retention and avoiding leakage of the radioactive material. To standardize the procedure, instillation of volumes higher than 200 ml are not recommended because only the terminal portion of the colon, responsible for the intestinal emptying, should be studied. Higher volumes tend to ascend to the proximal bowel, leading to erroneous results. To minimize this artifact, the patients are asked to stand up for 15 minutes before the evacuation to allow the deposition of the artificial feces in the final portion of the bowel to be more easily evacuated.

The patient should return to the examination room immediately after evacuating and feeling that the rectum is empty. This is important particularly in patients with frequently fragmented feces who tend to wait for another filling of the terminal bowel, a condition that may require a long time and interfere with the protocol.