Review / Derleme The importance of stool tests in diagnosis and follow-up of gastrointestinal disorders in children Çocuklarda sindirim sistemi hastalıklarının tanı ve izleminde dışkı incelemelerinin yeri Erhun Kasırga Division of Pediatric Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, Celal Bayar University Faculty of Medicine, Manisa, Turkey Cite this article as: Kasırga E. The importance of stool tests in diagnosis and follow-up of gastrointestinal disorders in children. Turk Pediatri Ars 2019; 54(3): 141–8. Abstract Öz Stool is not just a simple waste material. Some stool tests can be Dışkı yalnızca basit bir atık değildir. Bazı dışkı testleri sindirim sistemi easily used in primary care in the differential diagnosis of disorders enfeksiyonları, malabsorpsiyon sendromları ve inflamatuvar bağırsak such as gastrointestinal infections, malabsorption syndromes, and hastalıkları gibi hastalıkların ayırıcı tanısında birinci basamak sağlık inflammatory bowel diseases. Stool tests can prevent unnecessary hizmetlerinde kolaylıkla kullanılabilir. Dışkı testleri sayesinde gerek- laboratory investigations. Stool analyses include microscopic ex- siz laboratuvar incelemeleri önlenebilir. Dışkı incelemeleri arasında amination, chemical, immunologic, and microbiologic tests. Stool mikroskobik inceleme, kimyasal, immünolojik ve mikrobiyolojik test- samples can be examined for leukocytes, occult blood, fat, sugars ler vardır. Dışkı örneği; lökosit, gizli kan, yağ, indirgeyici maddeler (reducing substances), pH, pancreatic enzymes, alpha-1 antitrypsin, olarak adlandırılan şekerler, pH, pankreas enzimleri, alfa-1 antitripsin, calprotectin, and infectious causes (bacteria, viruses, and parasites). kalprotektin ve enfeksiyöz nedenler (bakteri, virüs ve parazitler) açı- Stool should also be macroscopically checked in terms of color, con- sından incelenebilir. Dışkı renk, kıvam, miktar, şekil, koku ve mukus sistency, quantity, shape, odor, and mucus. varlığı açısından da makroskobik olarak kontrol edilmelidir. Keywords: Children, gastrointestinal disorders, stool tests Anahtar sözcükler: Çocuklar, dışkı testleri, sindirim sistemi hastalıkları Introduction Macroscopic examination of the stool Important information about diseases that affect the Stool samples should be evaluated macroscopically in gastrointestinal system can be obtained with stool ex- terms of color, consistency, quantity, form, odor, and aminations. Stool can be examined macroscopically, presence of mucus. The presence of a small amount of microscopically, chemically, immunologically, and mi- mucus in stool is normal. However, the presence of co- crobiologically. Stool samples to be examined should be pious mucus or bloody mucus is abnormal. The normal collected in a clean container, fresh or kept under appro- color is tawny due to the presence of bilirubin and bile. priate conditions. In infants, the stool may be green, its consistency may be watery or pasty. Stool color varies greatly depending on The aim of this review was to present the most up-to- diet. Clay-colored or putty colored stool is observed in bil- date information about stool tests that have an important iary obstructions. If more than 100 mL blood is lost from place in the diagnosis and follow-up of childhood gas- the upper gastrointestinal system, black, tarry stool is ob- trointestinal diseases. served. Besides bleeding, black-colored stool may also be Corresponding Author / Sorumlu Yazar: Erhun Kasırga E-mail / E-posta: [email protected] Received / Geliş Tarihi: 28.05.2018 Accepted / Kabul Tarihi: 24.07.2018 ©Copyright 2019 by Turkish Pediatric Association - Available online at www.turkpediatriarsivi.com ©Telif Hakkı 2019 Türk Pediatri Kurumu Dernegi - Makale metnine www.turkpediatriarsivi.com web adresinden ulasılabilir. DOI: 10.14744/TurkPediatriArs.2018.00483 OPEN ACCESS This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. 141 Kasırga E. The importance of stool tests in childhood Turk Pediatri Ars 2019; 54(3): 141–8 observed due to iron or bismuth treatment. Red-colored Abnormal stool colors stool is observed in lower gastrointestinal tract bleeding. It has been shown that evaluation of stool color using a ‘stool color card’ in newborn babies (Fig. 1) increases awareness of biliary atresia (1, 2). The Modified Bristol vis- ual stool scale, which evaluates stool consistency (Fig. 2), has been found to be beneficial in monitoring treatment efficiency in functional constipation (3). Microscopic examination of the stool The most important step in the detection of stool abnor- malities and intestinal problems is microscopic exami- Normal stool colors nation of the stool. Microscopic examination is a diag- nostic tool for defining protozoa, helminths, and fecal leukocytes. Erythrocytes and leukocytes are not observed in normal stool. In order to see leukocytes, examinations should be performed in stool samples obtained from the area with mucus. Leukocytes are generally observed in Figure 1. Stool color card used for screening biliary atresia bacterial infections. They are not observed in diarrheas in infants caused by viruses and parasites. The presence of leuko- cytes in the stool is not a sensitive test in the diagnosis of inflammatory diarrhea because its ability to detect in- Separate firm lumps, like goat stool (very difficult to extract) flammatory diarrhea varies greatly (4). For moving organisms, fresh stool can be examined im- mediately. If it is not possible to examine the stool im- In the form of sausage, but lumpy mediately, it may be kept in 10% formalin for helminths and protozoa. The smallest amount of stool required for examination is 2–5 grams. At least three consecutive stool In the form of sausage or snake, soft and smooth samples are required for the examination of parasites. Contamination of stool with urine should be avoided. Giardia can be detected in a single sample in 50–70% of cases and in a third sample in 90%. In the diagnosis of Bulgy pieces with irregular borders, intestinal amoebiasis, cysts and trophozoites belonging pulpy to Entamoeba histolytica (E. histolytica) are investigated through microscopy examinations. However, the person who performs this examination should be an expert in Watery, no solid piece is found this area. In addition, microscopy examinations cannot differentiate E. histolytica strains from Entamoeba dis- Figure 2. Modified Bristol stool scale par (E. dispar) and Entamoeba moshkovskii strains. Three samples may be needed to be sent on separate days to de- compared with microscopy examinations in the diagnosis tect infection because excretion of cysts and trophozoites of Giardia, Cryptosporidium, and Entamoeba infection (5). is variable. The samples are intensified and stained with iodine in order to detect cysts. Staining with iron hema- Occult blood in the stool toxylin and/or Wheatley trichrome should be performed In peroxidase-based tests, peroxidase-like activity of to search for trophozoites. In invasive intestinal amoe- hematin and/or hemoglobin transforms the catalyzer biasis, blood is generally present in stool samples. The to blue. A restrictive diet may not be needed during the presence of phagocyted erythrocytes is not diagnostic for test. A systematic review demonstrated that sticking to a E. histolytica infection. Phagocyted erythrocytes may also restrictive diet did not decrease the rate of occult blood be seen with E. dispar. Leukocytes may not always be ob- positivity. Iron preparations ingested orally do not cause served in the stool because they may be disintegrated by a positive hemoccult test. Ingestion of large amounts of parasitic organisms. A rapid antigen test is more useful vitamin C causes false-negative results and intake of vi- 142 Turk Pediatri Ars 2019; 54(3): 141–8 Kasırga E. The importance of stool tests in childhood tamin C should be limited to less than 250 mg daily for ables estimation of daily fecal weight. This is generally at least three days before sampling. Before examination, higher than 200 g/day in patients with steatorrhea. Pa- stool samples should not be diluted again. Dilution in- tients should consume 70–120 g fat daily for an accurate creases the test’s sensitivity, but causes an increase in false- estimation. More than 6 g/day fat in the stool is patholog- positive results. Aspirin and non-steroidal anti-inflamma- ical. In patients with steatorrhea, however, more than 20 g tory drugs may lead to false positivity by causing minor fat is generally found in the stool daily. The test does not bleeding in the gastrointestinal mucosa. In addition, the give an accurate result if less than 60 g fat is consumed test should be repeated with two samples daily for three daily (8). days to increase the test’s accuracy. A loss of about 2–5 mL blood daily is normal in the intestines. Hemorrhages The percentage of absorbed fat (fractional fat absorption) above this limit can be detected in the hemoccult test (6). can be calculated after determining the mean daily fat in- Immunohistochemical occult blood tests were developed take. Fractional fat absorption is calculated with the fol- in order to measure human hemoglobin directly in the lowing formula: stool using monoclonal or polyclonal antibodies against the globin part of the human hemoglobin. It has high sen- (Fat intake - fat excreted)/fat intake x 100. sitivity and specificity in detecting lower gastrointestinal The percentage for normal fractional fat absorption is hemorrhages. In upper