1. Introduction
Obstetric acute kidney injury (AKI) is a sudden and temporary alteration of renal function during pregnancy or during the peripartum period [1] [2] . Its incidence in developed countries has fallen due to improvements in prenatal monitoring and early detection of pregnancy complications [2] [3] . On the other hand, in developing countries, pregnancy is responsible for 20% to 25% of the occurrence of AKI [4] . Obstetric AKI is complicated by heavy maternal morbidity and mortality [5] . The incidence of AKI during pregnancy was 16% (96 patients) of women admitted to the intensive care unit [6] . The main etiologies are represented by preeclampsia, HELLP syndrome and retroplacental hematoma [7] . Preeclampsia represents one of the leading causes of maternal and neonatal mortality and morbidity in developing countries [8] . According to the Chad Demographic and Health and Multiple Indicator Survey (EDS-MICS 2014 2015), Chad had one of the highest maternal mortality rates in Africa, with a ratio of 860 deaths per 100,000 births alive, which represents almost 45% of all deaths among women aged 15 - 49 [9] . Among the causes of this maternal mortality, obstetric AKI remains poorly appreciated. This is how we conducted this study with the aim of determining the epidemiological, etiological, therapeutic and progressive profiles of obstetric AKI.
2. Methodology
This was a cross-sectional study with descriptive and analytical aims over a period of 6 months from June 1, 2020 to November 30, 2020 and carried out in the Gyneco-Obstetric Emergency Department of the Mother and Child University Hospital (CHU-ME) of N’Djamena. All pregnant women with more than 20 weeks of amenorrhea until the immediate postpartum period, hospitalized in the obstetric emergency room of the “Mother and Child” University Hospital Center of N’Djamena in Chad, for acute renal failure diagnosed according to the KDIGO 2012 criteria had been included in the study. These patients were then referred to emergency intermittent hemodialysis at the Nephrology Department of the Renaissance University Hospital Center. Parturient with chronic renal failure, AKI before 20 weeks of gestation and non-consenting patients were excluded from the study. For each patient included in the study, the study data was collected using a pre-established survey form. These data were socio-demographic (age, profession, level of study, area of residence), clinical data (medical and gyneco-obstetric history and clinical signs), paraclinical (biological examinations, renal ultrasound and urinary analysis) and the therapeutic data. The patients were called at 3 months for clinical and paraclinical follow-up. Those whose files needed to be completed for missing information had been summoned by telephone. The evolving modalities were noted for each patient included. The outcome was favorable when recovery of renal function was total or partial. Total recovery was assessed by a return to normal in baseline creatinine levels upon discharge from hospitalization. It was unfavorable in the event of progression to chronic renal failure or the occurrence of death. Obstetric AKI is defined according to the KDIGO classification summarized in Table 1. Pregnant or gestational hypertension is defined by a systolic blood pressure (SBP) ≥ 140 mm Hg and/or a diastolic blood pressure (DBP) ≥ 90 mm Hg, occurring after 20 weeks and disappearing before the end of the sixth week of pregnancy. Preeclampsia is defined by the association of pregnancy-induced hypertension with proteinuria (>0.3 g/24h). Eclampsia is an acute paroxysmal accident of vascular-renal syndromes of pregnancy defined from the clinical point of view by having a convulsion occurring by repeated attacks, followed by a comatose state. Oliguria is defined as diuresis < 300 ml/24 hours, anuria as diuresis < 100 ml/24 hours. Disseminated intravascular coagulopathy (DIC) is defined by the presence of thrombocytopenia < 100,000 mm3, a decrease in fibrinogen < 3 g/l, fibrin degradation products > 40 m/dl and a prolongation of overall times: TQ and TCA from 1.5 to two times. HELLP syndrome is retained as defined by Weinstein [3] : hemolysis: increase in indirect bilirubin with drop in hemoglobin, hepatic cytolysis and thrombocytopenia < 100,000 mm3. Pregnancy monitoring was regular if patients received at least 4 prenatal consultations during pregnancy.
The data collected were analyzed using Excel 2013 software, SPSS version 18.0 (Statistical Package for Social Sciences 18.0) and were presented in the form of tables and figures. Quantitative data are expressed as medians, means ± standard deviation and qualitative variables as percentages. The Chi-square test was used for the comparison of qualitative variables and the student t-test for the comparison of quantitative variables.
3. Results
During our work, 1238 patients were collected. Among them, 56 cases of obstetric AKI were included, representing a hospital prevalence of 4.5%. The average age was 26.10 ± 5.86 years (16 and 37 years). There were 42.9% of patients (n = 24) who were aged over 30 years. It was noted that 64.3% of patients (n = 36) lived in an urban area and 35.7% (n = 20) in a semi-urban or rural area. There were 82.1% (n = 48) housewives. Arterial hypertension was found as a history in 10.7% (n = 6). There were 42% (n = 24) primigravidas, 32.1% pauciparous (n = 18) and 25% multiparous (n = 14). Pregnancy monitoring was regular in 32.1% (n = 18) and irregular in 35.7% (n = 25). However, 67.8% patients (n = 38) had not had any prenatal consultation (Table 1). On admission, consciousness was altered in 32.1% patients (n = 18). Anuria was observed in 7.1% (n = 4) and oliguric in 28.6% (n = 16). There were 17.8% of patients (n = 10) who had a mucocutaneous pallor. Hypertension was found in 57.1% (n = 32) of patients. The 53.6% of patients (n = 30) had an edematous syndrome. By using a urine dipstick, 96.4% (n = 54) had proteinuria. Metrorrhagia was noted in 5.5% of patients (n = 3) and convulsions with tongue biting in 7.1% of patients (n = 4).
Biologically, the mean serum creatinine was 311.6 ± 302.9 µmol/l with (91 to 990 µmol/l). The average urea was 2.2 ± 4.4 g/l (0.2 to 3.5 g/l). The classification of AKI according to the severity stages of KDIGO is shown in Figure 1. Anemia was found in 50% of patients (n = 28) with an average hemoglobin level of 9.98 g/dl (5.2 and 17.3 g/dl). In 35.7% (n = 20), hepatic cytolysis was noted with a transaminase level greater than 5 times the normal. This cytolysis was related to thrombocytopenia (platelet level less than 100,000 mm3) as part of HELLP syndrome in 17.9% of patients (n = 10) and severe malaria with thick blood showing the presence of Plasmodium Falciparum in 17.9% of patients (n = 10). Renal ultrasound did not reveal any renal abnormality. Obstetric AKI was found in the 2nd trimester in 21.4%, in the 3rd trimester in 42.9% and postpartum in 28.6% of patients. Organic AKI due to acute tubular necrosis was noted in 52 cases. The causes of obstetric AKI are represented by preeclampsia in 60.7%, HELLP syndrome in 17.9% and hemorrhagic delivery which is complicated by a retroplacental hematoma in 7.1% (Table 2). Obstetrically, the pregnancy was progressive in 37.5% (n = 21) of cases. The pregnancy was terminated in 62.5% (n = 35), with a vaginal fetal extraction in 33.9% (n = 19) and by cesarean section in 28.5% (n = 16) of cases.
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Table 1. Socio-demographic characteristics of patients.
Eclampsia (n = 9), retroperitoneal hematoma (n = 4) and acute fetal distress (n = 3) were the main indications for cesarean delivery.
Calcium channel blockers were prescribed in 87.5% of patients (n = 61) and blood transfusion in 53.5% of patients (n = 30). Hemodialysis was indicated in 20 patients whose indications were acute lung edema (n = 8) and hyperkalemia (n = 3) which was refractory to medical treatment, poorly tolerated uremia (n = 5) and anuria for more than 48 hours (n = 4).
The average length of hospital stay was 9.2 ± 5 days (2 and 20 days). The outcome was favorable in 78.6% (n = 44) with a resumption of diuresis and total recovery of renal function (Figure 2). In 7.1% of patients (n = 4), recovery of renal function was partial with a mean serum creatinine varying between 185 - 219.7 µmol/l. We recorded 14.3% (n = 8) maternal deaths, linked to complications of AKI namely acute lung edema (n = 4); uremic encephalopathy (n = 2) and septic shock (n = 2). The fetal prognosis was marked by fetal death in utero in 37.5% (n = 21) cases. The 32.1% of newborns (n = 18) were hospitalized in neonatology, the indications for which were prematurity in 14.2% (n = 8), neonatal infection in 10.7% (n = 6) and perinatal asphyxia in 7.1% (n = 4) of cases.
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Table 2. Etiology of obstetric AKI (n = 56).
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Figure 1. Classification of obstetric AKI according to KDIGO.
4. Discussion
Limitations of the study were the small sample size and the difficulty of recruiting patients who lost their children due to AKI. The second problem concerns the difficulty of obtaining a place on dialysis because there are only 2 dialysis centers in N’Djamena. The present study carried out in Chad demonstrated that obstetric AKI constitutes 4.52% of pregnancy and immediate postpartum complications. The prevalence of obstetric AKI varies depending on the series and the causes. In Sub-Saharan Africa, it still remains high compared to developed countries [4] [10] [11] . In the sub-region, particularly in Niger [12] , the hospital prevalence was around 14.94%, while in Senegal [13] and Algeria [14] , it was 4.65% and 29%, respectively. The lack of prenatal monitoring through early detection of pregnancy complications would largely explain this high prevalence. The majority of patients were young primigravidas (40%), more than a third of whom were rural. This would explain the absence of regular prenatal consultation (67.8%). Primigravida is a risk factor for preeclampsia due to immunological intolerance of certain elements of the sperm, and insufficient attendance at prenatal consultations increases the risk of pregnancy and postpartum complications [12] [15] [16] . Arterial hypertension was noted in more than half of cases and the discovery of proteinuria on the urine dipstick in almost all patients should prompt a search for these markers in pregnant women from the 2nd trimester in order to prevent complications of preeclampsia. Preeclampsia is often the main cause of organic AKI [11] [13] [17] . The frequency of preeclampsia varies depending on the series with 19% and 67.2%, respectively [11] [18] . In the series by Mahamat Abderraman et al., in a study involving 3067 parturient patients, the prevalence of preeclampsia represented 2.6% of all pregnancies [15] . In our study, it was found in 60.7% of patients, like other African studies [12] [19] . Other risk factors for the occurrence of obstetric AKI are HELLP syndrome and retroplacental hematoma. In Niger, Yaya et al. found 15% with retroplacental hematoma complicating preeclampsia [12] , while in our series, it was observed in 7.1% of patients. The endothelial damage of preeclampsia, the activation of coagulation and the obstruction of renal vessels explain this constant renal damage. In general, HELLP syndrome, disseminated intravascular coagulation and retroplacental hematoma cause obstetric AKI and when this triad is associated with hemorrhagic shock or amniotic embolism, this will increase the risk of cortical necrosis [2] . In Morocco, in a 5-year observational study that included 356 patients with HELLP syndrome, 31.7% (n = 113) developed AKI. Dialysis was used in 36 patients. Recovery of renal function was noted in 85% of patients, persistence of chronic kidney disease in 12.4% of patients (n = 14) and maternal death in 14.2% (n = 16) of patients [7] . These vascular complications are all the more formidable as the patients present with anemia which was found in half of the patients. Hemodialysis was initiated in 25% of patients (n = 14) in contrast to the high indication for dialysis. In our study, few had access to dialysis due to a lack of dialysis generators or family refusal who do not have confidence in this purification technique. The use of hemodialysis has been estimated between 70% - 100% in other studies [1] [11] [20] . The outcome is often favorable under hemodialysis. In a study carried out at Marocco in 2011, 17 out of 44 patients (38.6%) included had undergone dialysis with total recovery of renal function in 29 patients [21] . The cure rate in our series was much higher than that reported by other authors [13] [19] . Nevertheless, in our series, as in most developing countries [12] [13] , maternal mortality was high. This mortality would be attributed to septic shock and the delay in treating postpartum complications. According to a Tunisian study, a poorly managed pregnancy was significantly associated with a high rate of maternal mortality (p = 0.047 or 0.23 (0.05 - 1.09)). Complications statistically significantly associated with maternal mortality were disseminated intravascular coagulation (p = 0.012) and multiple organ dysfunction syndrome (p = 0.001) [6] . We deplore 24 cases of fetal death in utero. The fetal mortality found in a study carried out in Oujda in Morocco in 22 patients admitted for obstetric AKI was 17.3% [22] . Perinatal mortality remains high and reaches 43% in the literature [11] . Deaths were linked to perinatal asphyxia, sepsis and maternal complications. The lack of neonatal intensive care units and the lack of responsiveness to acute kidney injury would explain this neonatal mortality in Sub-Saharan Africa. Before 34 weeks, early termination of pregnancy is the cause of high perinatal morbidity and mortality. The pregnancy was terminated in 62.5% of patients (n = 35) in our study. The final treatment for preeclampsia remains termination of the pregnancy and delivery of the placenta. This obstetric treatment can cause fetal complications such as prematurity or maternal complications (eclampsia, HELLP syndrome, retroplacental hematomas), requiring close monitoring and stopping expectancy at the slightest sign of maternal or fetal seriousness. Termination of pregnancy should be considered from 38 weeks, without precipitation, in order to reduce maternal and infant deaths [8] .
5. Conclusion
Obstetric AKI remains a serious complication of pregnancy and postpartum. Despite the good renal prognosis, fetal-maternal morbidity and mortality remain high in developing countries and severe preeclampsia constitutes the main cause. The use of hemodialysis has improved maternal and fetal prognosis. Improving patient care and prognosis requires adequate perinatal consultations with good monitoring of clinical and biological, such as blood and urine indicators. Emphasis must be placed on mandatory monitoring of pregnancies and early management of complications.
Abbreviations
AKI: acute kidney injury; PE: preeclampsia.