The use of semi-quantitative tests at Cesarean section delivery for the differentiation of canine fetal fluids from maternal urine on the basis of biochemical characteristics

Abstract

In dogs, there is no diagnostic test to identify and differentiate fetal fluids from maternal urine in the event that a clear-yellowish vulvar discharge is observed pre-whelping. The objective of this study was to find a test that could easily and accurately identify rupture of the fetal membranes preceding parturition. Maternal urine, and amniotic fluid (AMF) and allantoic fluid (ALF) from only one fetus per bitch, were collected intraoperatively during Cesarean section. Specific gravity (SG) was analyzed with a refractometer, whereas the presence of leukocytes, protein, glucose, ketones, bilirubin, urobilinogen, nitrite, erythrocyte/hemoglobin (Hb), and the pH were assessed using a urine dipstick (Combur-Test). Combined calcium and magnesium (Ca/Mg) content were evaluated with the Total Hardness Test. The AmniSure test, which detects rupture of fetal membranes in women on the basis of the presence of human placental alpha microglobulin-1, was also performed on canine AMF, ALF, and urine. Data were analyzed using the Fisher's exact test, Wilcoxon signed-rank test, and Pearson's correlation. Sensitivity, specificity, and positive and negative likelihood ratios (LR) were calculated for parameters with significant difference between urine and both fetal fluids. Maternal urine had higher SG and lower leukocyte, protein, Hb, and Ca/Mg content than AMF and ALF. Glucose was more often present in AMF (n = 17) and ALF (n = 12) than in urine (n = 1), whereas ketone bodies were rarely detected in ALF compared with urine. Bilirubin content was higher in urine and ALF than in AMF. AMF pH was less variable and higher than the pH of ALF or urine. The AmniSure was negative in all samples tested. Sensitivity and specificity for SG and for the detection of leukocytes, protein, glucose, Hb, Ca/Mg, and glucose without ketones in urine and fetal fluids were between 42% to 100% and 65% to 100%, respectively. Best positive LR was achieved for the detection of glucose without ketones and best negative LR for SG of 1.022 or less. In conclusion, the AmniSure test, which is used in humans with high diagnostic accuracy, cannot identify AMF and ALF in dogs. On the basis of our results in 26 dogs undergoing Cesarean section, the presence or absence of fetal fluids could be best determined by a positive glucose test without ketone bodies or by SG higher than 1.022, respectively. These tests may serve as additional tools to recognize parturition if clear-yellowish vulvar discharge is present in a term pregnant bitch, but their accuracy and practicability in the clinical setting need to be confirmed.

Clinical Trial on the Usefulness of On-Site Evaluation of Canine Fetal Fluids by Reagent Test Strip in Puppies at Elective Caesarean Section

“…In 2021, Tal et al [ 5 ] demonstrated the possibility to easily and safely perform amniocentesis in anesthetized bitches at around 35–62 days of pregnancy. Moreover, at the time of parturition, when caesarean section is performed, fetal fluids (amniotic and allantoic) can be easily and securely sampled, as demonstrated by many studies [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. Other than that, the canine fetal fluids were also useful for mesenchymal stem cells isolation and growth as a model of these cell’s biology study and for possible therapeutic application [ 19 , 20 ].…”

Urinalysis in Great Dane Puppies from Birth to 28 Days of Age

“…They were immediately evaluated by commercial dipsticks (Combur-Test ® , Roche Diagnostic Limited, Mannheim, Germany) for SG, pH, leukocytes, nitrites, glucose, proteins, ketones, urobilinogen, bilirubin, and blood. Following the technique reported by Balogh et al [4], a drop of urine was put on each field of the strip and, after dripping, the results were read after 60 seconds for all the parameters, except for leukocytes that were read at 120 seconds. For each parameter, the results were recorded using the visual reference colorimetric scale reported by the company ( Table 1).…”

“…Few studies looked for markers of neonatal homeostasis, but they still cannot be widely applied in everyday veterinary clinical practice: lactate, glucose and beta-hydroxybutyrate levels were correlated to neonatal mortality [3]; the Combur test analysis on glucose and ketones in the fetal fluids collected at C-section was described [4]; the composition of the fetal fluids at C-section was linked to neonatal mortality and viability [5].…”

“…Dipstick urinalysis is easily performable under every condition, is a cheap and repeatable diagnostic test, providing immediate results. Moreover, as reported by Balogh et al [4], a drop of urine can be put on each field of the strip to obtain reliable results using small volumes of urine. Thanks to their advantages, dipstick tests are, therefore, widespread in veterinary companion animals' clinical practice.…”

“…Urinalysis dipsticks were reported to be useful also in canine perinatology. In a first study, Faulks and Lane [7] reported data on urinalysis in 0-24-week-old puppies, while more recently, Balogh et al [4] used dipstick to differentiate maternal urines from amniotic and allantoic fluids at the beginning of parturition, in dogs. On the other hand, dipstick tests do not analyze either sediment or bacteria.…”