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Keywords:

  • abdominal ultrasound;
  • Cesarean section;
  • postoperative;
  • postpartum

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References

Objectives

To describe prospectively the normal abdominal and pelvic ultrasound features within 24 h following uneventful Cesarean section.

Methods

Transabdominal ultrasound examination was performed between 1 and 3 h, and again at 24 h, following lower-segment Cesarean section (LSCS). The myometrium, endometrium, and amount and distribution of free peritoneal fluid were studied in 30 women with singleton pregnancies who underwent LSCS delivery.

Results

Examinations were performed easily in all cases except one who was morbidly obese (body mass index > 40 kg/m2). At 1–3 h after delivery, mean ± SD endometrial thickness was 13 ± 2 mm. Mean uterine length, from the fundus to the cervical external os, was 160 ± 15 mm. Measurement of uterine length in the mid-sagittal plane of the pelvis was impossible in eight cases (27%) owing to pain. No abnormal intrauterine findings were observed. Mean uterine width was 110 ± 10 mm. Mean distance between the sacral promontory and uterine fundus was 104 ± 11 mm. Mean thicknesses of the anterior and posterior walls of the uterus were 40 ± 5 mm and 39 ± 7 mm, respectively. No fluid was seen in Morrison's or Douglas' pouches. There was a consistent and significant reduction between the measurements performed at 1–3 h and those at 24 h after LSCS, except for the distance between the fundus and external os.

Conclusions

Ultrasound examination is feasible after Cesarean section. Images are obtained easily, even when scanning through the scar. In normal pregnancies, there is no fluid in the abdomen or pelvis. These results could help clinicians in the decision-making process in cases of early postpartum hemorrhage or hemodynamic instability following LSCS. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References

Cesarean delivery is associated with an increased risk of postpartum blood loss and related morbidity compared with vaginal delivery1, 2. The management of early post-Cesarean section hemorrhage could benefit from ultrasound examination to detect blood collections within the uterus or in the abdominal cavity, and to guide further therapy. Several authors have described ultrasound findings a few days after Cesarean delivery and their correlation with postoperative morbidity3–5. However, none of these studies has described ultrasound findings in the abdominal cavity early after Cesarean section.

Management of postpartum hemorrhage involves a wide range of medical and surgical tools, ranging from oxytocin or prostaglandin infusion to arterial embolization and surgical procedures. The latter range from uterine wall or arterial ligations to hysterectomy6. National guidelines from the UK and France specifically address management of postpartum hemorrhage following Cesarean section. Surgical procedures are recommended as the first-line treatment in France, but arterial embolization is preferred in the UK guidelines7, 8. A better knowledge of the normal ultrasound features of the postpartum abdomen and pelvis in asymptomatic women following uneventful Cesarean section may help in choosing the first-line treatment in difficult cases.

The aim of this prospective study was to evaluate the feasibility of ultrasound examination and to describe normal abdominal and pelvic ultrasound features in 30 women, 1–3 h as well as 24 h following uneventful pregnancy and Cesarean section.

Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References

This prospective observational study was conducted between January 2007 and April 2007 in one center. We included women within 3 h following uneventful Cesarean delivery of a singleton baby at term. Uneventful Cesarean delivery was defined using the following criteria: singleton pregnancy, more than 37 weeks of gestation, no postpartum hemorrhage, no use of prostaglandins, and no associated surgical procedures during or following the Cesarean section. We based our study on a sample size of 30 individuals, which is the normal range of a homogeneous group according to the central limit theorem9.

Before performing the first ultrasound examination, each patient was examined clinically by the operator in order to evaluate postpartum bleeding. Before performing the second ultrasound examination, the operator confirmed that blood transfusion, further surgery or embolization was not required. All scans were performed and interpreted by two physicians (M.K. and J.N.), using a portable ultrasound device (Logiq Book XP ultrasound system, General Electric Medical System, Ultrasound and primary care diagnostic, Gif sur Yvette, France) with a 4-MHz curvilinear array transducer. Five procedures were initially performed to define three standard planes to be obtained following Cesarean section. These cases were considered as preliminary investigation and were not included in the subsequent analysis. Transabdominal ultrasound imaging was performed once between 1 and 3 h, and again at 24 h after Cesarean delivery in all cases.

Standard planes

Mid-sagittal plane of the uterine corpus (Figure 1)

Landmarks included the endometrial stripe, most of the uterine corpus (including the uterine fundus), the sacral promontory and at least two lumbar vertebrae (L4 and L5). Measurements included the distance between the uterine fundus and promontory, and between the uterine fundus and vertebra L5 (for these the calipers were positioned on the point where a line extrapolated from the endometrial stripe intersected with the uterine fundus and on the anterosuperior point of the vertebral body); thickness of the anterior and posterior uterine walls, measured halfway between the uterine fundus and the cervix; and endometrial thickness.

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Figure 1. Ultrasound image (a) and schematic diagram (b) of the mid-sagittal plane of the uterus, showing sites for measurement of the distances between the uterine fundus and promontory (E, distance I) and vertebra L5 (D, distance J), thickness of the anterior (A) and posterior (C) uterine walls, endometrial thickness (B), and deepest vertical pool of fluid collection in the pelvic cavity (F).

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Mid-sagittal plane of the pelvis (Figure 2)

Landmarks included the whole uterus including the cervix, the balloon of the urinary catheter (when still in place) and the Cesarean scar. Measurements included the length of the uterus, from the external os of the cervix to the fundus and the depth of the vertical pool of fluid, if any, in the pelvic cavity. The crossbar of the calipers had to be positioned in order to measure the deepest vertical pocket (anterior to posterior) in the pelvic cavity.

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Figure 2. Ultrasound image (a) and schematic diagram (b) of the mid-sagittal plane of the pelvis, which allows measurement of uterine length. A, anterior uterine wall; B, endometrial thickness; C, posterior uterine wall; D, lumbar vertebra L5; E, sacral vertebra S1; F, Douglas pouch; G, uterine scar; H, balloon of urinary catheter.

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Parasagittal plane of Morrison's pouch (Figure 3)

The transducer was placed in the region of the right mid-axillary line in order to visualize the right upper quadrant at the interface between the liver and Gerota's capsule of the kidney.

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Figure 3. Ultrasound image of the parasagittal plane of the hepatorenal pouch HRP. L, liver; RK, right kidney.

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Statistical analysis

Data were analyzed using the paired t-test, Wilcoxon matched pairs test and Pearson's correlation after testing for normality (Shapiro–Wilk test). P < 0.05 was considered statistically significant.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References

The first ultrasound examination was performed in the recovery room at a mean interval of 107 (range, 60–180) min from the time of delivery. In one case the first clinical examination suggested active bleeding and this patient was subsequently excluded from the study. She underwent arterial embolization for postpartum hemorrhage. Ultrasound examination was performed but was not analyzed for this study. Demographics and Cesarean circumstances in the 30 cases included are shown in Table 1.

Table 1. Demographic data and indications for Cesarean delivery in the 30 women scanned
ParameterValue
  1. CTG, cardiotocography.

Interval between first ultrasound examination and time of delivery (min, mean (range))107 (60–180)
Mean maternal age (years, mean (range))31.7 (21–43)
Parity (median (range))2 (1–5)
Birth weight (g, mean ± SD (range))3139 ± 529 (2130–4170)
Indications for Cesarean section (n (%)) 
 Elective18 (60)
Repeat elective Cesarean section12 (40)
Breech presentation5 (17)
History of severe anal sphincter1 (3)
 lesion during previous delivery 
 During labor12 (40)
Non-reassuring fetal CTG10 (33)
Obstructed labor2 (7)

All Cesarean sections were performed using a low transverse incision followed by either Pfannenstiel, Joel–Cohen or Mouchel techniques10, 11. Transverse segmental uterine incision was performed directly above the bladder fold. Removal of the placenta was spontaneous in 29 cases and performed manually in one case. Manual examination of the uterine cavity was performed in all cases. The uterus was exteriorized in seven cases and left intra-abdominally in 23 cases. Placental remnants and blood clots were removed from the uterine cavity, and lateral and posterior abdominal spaces using absorbent gauze sponge. Closure of the uterus was performed with a single layer of absorbable suture (Vicryl number 1, Ethicon France, Issy Les Moulineaux, France). We did not perform any intra-abdominal irrigation or drainage. No peritoneal suture was performed. The rectus aponeurosis was sutured using a single layer of Vicryl number 1. Staples were used for skin closure. Oxytocin infusion (50 units in 500 mL) was given over the first 6 h following surgery in all cases and the bladder was left catheterized for 2 h after surgery.

All ultrasound examinations were performed easily and standard planes were obtained in all cases except for one patient who was morbidly obese (body mass index > 40 kg/m2).

First ultrasound examination (1–3 h after Cesarean section)

No intrauterine abnormalities or blood clots were observed. Measurement of the uterine length in a mid-sagittal scan of the whole pelvis (Figure 2) was impossible to obtain in eight cases (27%) owing to pain. Other planes were obtained easily and the Cesarean scar did not interfere with the ultrasound examination. No fluid was seen in the hepatorenal pouch (Morrison's) or in the rectovaginal excavation (Douglas'), whether the uterus had been exteriorized or not.

Measurements of endometrial thickness and of the anterior and posterior walls were performed easily. The distance from the uterine fundus to the L5 vertebra was more easily obtained than the distance from the uterine fundus to the promontory (Figure 1).

Measurements obtained during the first ultrasound examinations are shown in Table 2. All measurements were normally distributed, except for the posterior wall thickness at mid-length. There was no significant difference in measurements between Cesarean sections performed during labor or electively.

Table 2. Comparison of uterine measurements obtained during the first and second ultrasound examinations
ExaminationEndometrial thickness at mid-length of corpus uteri (mm)Distance between fundus and external os (mm)Uterine width at mid-length of corpus uteri (mm)Distance between vertebra L5 and fundus (mm)Distance between promontory and fundus (mm)Anterior wall thickness at mid-length (mm)Posterior wall thickness at mid-length (mm)
  • Data expressed as mean ± SD unless otherwise noted.

  • *

    Paired t-test.

  • Wilcoxon matched pairs test.

  • Number of women in whom both examinations could be performed.

First ultrasound examination13 ± 2160 ± 15110 ± 1068 ± 7104 ± 1140 ± 539 ± 7
Second ultrasound examination10 ± 2155 ± 13101 ± 1062 ± 694 ± 1134 ± 535 ± 5
P< 0.0001*0.0523 *< 0.0001*< 0.0001*< 0.0001*< 0.0001*0.0016
Number of pairs29172929292929

Second ultrasound examination (24 h after Cesarean section)

Findings were similar at 24 h after delivery, but in one case a heterogeneous mixed-density mass of 70 × 36 mm was seen in the uterus (Figure 4) of a 36-year-old woman who had completed her second pregnancy (and had a Cesarean section for the first delivery). She opted for elective Cesarean section for her second delivery and delivered a 3950-g baby. She did not experience abnormal bleeding and her hemoglobin level was still stable at 8 weeks postpartum. No action was undertaken.

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Figure 4. Ultrasound image obtained 24 h after Cesarean section showing an intrauterine heterogeneous mass (70 × 36 mm) of mixed echodensity.

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Measurements are shown in Table 2. Measurement of uterine length was impossible in nine cases because of pain. Mean endometrial thickness at mid-length of the corpus uteri was significantly smaller when Cesarean section was performed during labor than when Cesarean section was elective (9.1 mm vs. 10.7 mm, P = 0.02). Mean anterior wall thickness at mid-length was larger when Cesarean section was performed during labor than when it was elective (35.6 mm vs. 32.3 mm, P = 0.04).

Comparison between the first and second ultrasound examinations showed a significant decrease in all measurements, except for the distance between fundus and external os (Table 2).

Correlation between birth weight, parity and ultrasound measurements

There was a significant correlation between birth weight and posterior wall thickness at mid-length on first ultrasound examination (r = − 0.4679; 95% CI, − 0.7123 to − 0.1223; P = 0.01). There was a significant correlation between parity and distance between the sacral promontory and fundus on second ultrasound examination (r = 0.4509, 95% CI, 0.1010–0.7015; P = 0.01).

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References

We have described normal abdominal and pelvic ultrasound images early after Cesarean section. Ultrasound examination was feasible in all but one case and images were obtained easily using three standard planes. No fluid could be visualized in the abdomen or in the pelvis. Our findings could help clinicians in the decision-making process in cases of early postpartum hemorrhage or hemodynamic instability following lower-segment Cesarean section (LSCS). Images were obtained by two physicians, and details of surgery as well as peripartum management were known and taken into account in the subsequent analysis.

During the first examination pain did not interfere with the examination when scanning through the scar, probably because of the remaining effect of spinal anesthesia. However, measurement of uterine length, which requires strong pressure to be applied on the fundus, was painful and this measurement could not be obtained in 27% of cases during the first scan and in 30% of cases during the second scan. Moreover, this pressure could artificially reduce the uterine length. Therefore, measurement of the distance from the L5 vertebra to the uterine fundus in the mid-sagittal plane of the uterus seems preferable.

Several authors have described routine ultrasound findings of the uterus following vaginal delivery (Table 3). Lipinski and Adam performed ultrasound examination within 24 h after delivery and described three types of postpartum uterus: empty uterus, cavity separation indicative of blood or clot, and dense cavity echoes representing retained tissue12. Carlan et al. described retained products of conception immediately after placental delivery13. Sokol et. al performed ultrasound examination within 48 h following vaginal delivery14. Echogenic material was seen in the endometrial cavity in 40% of asymptomatic patients. Edwards and Ellwood described the presence of an endometrial echogenic mass in 51%, 21% and 6% at 7, 14 and 21 days postpartum, respectively15.

Table 3. Summary of the literature on diagnosis of intrauterine retained products by ultrasound examination following uneventful vaginal delivery
ReferencenInterval between ultrasound examination and deliveryUltrasonographic definition of ‘retained product’Retained products on ultrasound (n (%))Documented retained products of conceptionPredictive values of ultrasonography in diagnosis of retained placental tissue
  1. NPV, negative predictive value; PPV, positive predictive value.

Carlan et al. (1997)13131 (127 with fullyWithin 5 min after placentalEchogenic or19 (15)24 (18%) (systematic manualPPV 58% (11/19)
  interpretable images) delivery heterogeneous mass  exploration and spongeNPV 88% (95/108)
      curettage) 
Sokol et al. (2004)1440Within 48 h after normal vaginal deliveryHyperechogenic images16 (40)No systematic aspiration or curettage 
Edwards and Ellwood (2000)15407 days after vaginal deliveryHyperechogenic images− (51)No systematic aspiration or curettage 
Lipinski and Adam (1981)12100Within 24 h after normal vaginal deliveryHyperechogenic images10 (10)No systematic aspiration or curettage 
Deans and Dietz (2006)2294 (92 after vaginal delivery)Within 24 h after normal vaginal delivery (92 patients) or Cesarean section (2 patients)Upper segment thickness > 15 mm30 (32)No systematic aspiration or curettage 

We observed material in the uterine cavity in only one case (Figure 4). The comparatively low incidence is likely to be due to systematic manual examination of the uterine cavity following placental delivery during surgery. The only case of intrauterine collection in our series had an uneventful outcome. This is consistent with the findings summarized above, demonstrating that the diagnosis of intrauterine retention provided by ultrasonography is not specific and has little, if any, clinical significance13–15.

Several studies have focused on ultrasound findings of the post-Cesarean abdomen and their correlation with morbidity days after the operation. Burger et al. first described ‘fluid filled areas anterior to the site of the wound between the uterus and the bladder’, speculating that these areas might represent collections of blood or fluid4. This was reported in up to 29% of women after Cesarean section by Faustin et al. and was more likely to occur when surgery exceeded 90 min, blood loss was above 1000 mL and when blood transfusion was required5. In cases where the bladder flap hematoma was larger than 3 cm, women were more likely to develop postoperative morbidity as reflected by high temperature, hospital stay exceeding 8 days and the need for antibiotics. The significance of these findings remains unclear16, 17. In our series of uncomplicated surgery none of these aspects was noted within 24 h after surgery. We did not investigate ultrasound features later in the postpartum period and we cannot compare our findings with those published in the literature. Furthermore, in our series, suture of the peritoneum was not performed during Cesarean section.

Only one study, by Antonelli et al., has focused on sonographic detection of fluid collection following Cesarean section and described it as a frequent finding, occurring in 48% of cases 4 days following Cesarean section. Most fluid collections described in the study were observed in the abdominal wall, not in the peritoneal cavity. Antonelli et al. described only two cases with free fluid in the abdominal cavity among 145 women (1.4%), which could explain why we did not observe peritoneal free fluid in our study population.

In our series, none of the 30 ultrasound examination after LSCS showed fluid in either Douglas' or Morrison's pouches. The explanation for this might be the absence of peritoneal irrigation and systematic intra-abdominal cleaning after closure of the uterine incision. We therefore consider that fluid detection should be considered abnormal, especially in cases with unstable hemodynamics (hypotension, tachycardia or malaise) or abnormal vaginal bleeding. These findings may influence management towards a more surgical approach.

One of the three cases reported by Rodriguez et al. supports this theory18. Ultrasound examination of the abdomen following Cesarean section showed free peritoneal fluid in a hypotensive and oliguric 20-year-old woman. This fluid was initially thought to be secondary to irrigation at Cesarean section, but repeat ultrasound examination showed increased peritoneal free fluid and exploratory laparotomy confirmed intra-abdominal hemorrhage.

Most studies on ultrasound examination of the postpartum uterus did not provide uterine dimensions. Edwards and Ellwood attempted to define the ultrasound appearance of the uterus following uncomplicated postpartum recovery after vaginal delivery15. Uterine volumes were obtained, but uterine measurements were not reported. Sokol et al. performed transabdominal ultrasound examination within 48 h after vaginal delivery14, and reported a mean ± SD endometrial thickness of 1.1 ± 0.6 cm, uterine length 16.1 ± 1.7 cm and uterine thickness 8.7 ± 1.0 cm. Our data are similar to those reported by Sokol et al., but the exact timing of their measurements after delivery was not mentioned. In 56 patients with postpartum hemorrhage, Lee et al. reported uterine dimensions that were 20% larger than ours but no ultrasound images were provided in the paper19.

Shalev et al. investigated 120 patients 3 days after vaginal or Cesarean delivery and found that uterine length was significantly larger following Cesarean section compared with vaginal delivery (22.2 cm vs. 17.2 cm, P = 0.0001)20. The anterior wall was also found to be significantly thinner than the posterior wall (39 mm vs. 46 mm, P = 0.0001). Uterine length measurements were higher than those in our series, whereas measurements of both the anterior and posterior uterine walls were similar. Measurement of uterine length from the fundus requires strong pressure to be applied on the uterus, which could artificially reduce its length. Measurement of the distance between the L5 vertebrae and the uterine fundus seems therefore to be more informative and is less painful. Other explanations for these discrepancies in uterine measurements may include parity, differences in surgical techniques, improvement in ultrasound technology and dose of oxytocin after Cesarean section, which may differ from that given after vaginal delivery.

In conclusion, although ultrasonography has become a useful tool during the third stage of labor21, its role in early management after Cesarean section has still to be determined. This study suggests that ultrasound examination of the postpartum uterus and abdominal cavity may be useful in cases of early postpartum hemorrhage or hemodynamic instability following LSCS.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References
  • 1
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    Antonelli E, Morales MA, Dumps P, Boulvain M, Weil A. Sonographic detection of fluid collections and postoperative morbidity following Cesarean section and hysterectomy. Ultrasound Obstet Gynecol 2004; 23: 388392.
  • 4
    Burger NF, Darazs B, Boes EG. An echographic evaluation during the early puerperium of the uterine wound after cesarean section. J Clin Ultrasound 1982; 10: 271274.
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