Differential diagnoses of magnetic resonance imaging for suspected acute appendicitis in pregnant patients

doi:10.5847/wjem.j.1920-8642.2018.01.004

Abstract

Abstract:

BACKGROUND: Accurate and timely diagnosis of acute surgical disease in pregnant patient is challenging. Although magnetic resonance imaging (MRI) is the most accurate modality to diagnose acute appendicitis in pregnant patients, it is often used as a last resort because of high cost and long scan time. We performed this study to analyze differential diagnoses of appendix MRI and to investigate if there are any blood tests that can predict surgical condition in pregnant patients.
METHODS: A retrospective, cross-sectional study was conducted on 46 pregnant patients who underwent non-enhanced appendix MRI in suspicion of acute appendicitis from 2010 to 2016. Differential diagnoses of appendix MRI were analyzed and blood tests were compared between those who had surgical and non-surgical disease.
RESULTS: Appendix MRI differentiated two surgical disease; acute appendicitis and ovarian torsion; and various non-surgical conditions such as uterine myoma, hydronephrosis, ureterolithiasis and diverticulitis among clinically suspected acute appendicitis in pregnancy. The diagnostic accuracy of MRI for acute appendicitis in this study was 93.5%. Patients who had surgical disease showed significantly higher WBC count (≥11,000/mm³), proportion of neutrophils in the WBC (≥79.9%), neutrophil-to-lymphocyte ratio (NLR≥6.4), levels of C-reactive protein (CRP≥1.82 mg/dL) and bilirubin (≥0.66 mg/dL ) than those who had non-surgical disease.
CONCLUSION: MRI can reliably differentiate surgical conditions and several blood tests (WBC, proportion of neutrophils in the WBC, NLR, CRP, bilirubin) can help anticipate acute surgical condition among pregnant patients suspected to have acute appendicitis.

Key words: Appendicitis, Magnetic resonance imaging, Pregnancy, Neutrophils

Ji Yong Jung, Ji Ung Na, Sang Kuk Han, Pil Cho Choi, Jang Hee LEE, Dong Hyuk Shin. Differential diagnoses of magnetic resonance imaging for suspected acute appendicitis in pregnant patients[J]. World Journal of Emergency Medicine, 2018, 9(1): 26-32.

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Characteristics	Value
Number, n	46
Age, median (IQR)	31 (28, 34)
Gestational age, n (%)
First trimester	11 (23.9)
Second trimester	27 (58.7)
Third trimester	8 (17.4)
Location of pain, n (%)
Right lower quadrant	35 (76.1)
Suprapubic area	4 (8.7)
Periumbilical area	3 (6.5)
Right upper quadrant	2 (4.3)
Diagnostic procedure, n (%)
MRI only	29 (63.0)
MRI after ultrasonography	17 (37.0)

MRI report (Number, %)	Final diagnosis (Number)
Group 1: Normal appendix without other abnormal findings (18, 39.1%)	Unspecified abdominal pain (18)
Group 2: Normal appendix with other findings (10, 21.7%)	Non-surgical GI disease: enteritis (1), fecal impaction (1), diverticulitis (1) Non-surgical urinary disease: ureter stone (1), obstructive hydronephrosis (2) Non-surgical gynecologic disease: myoma red degeneration (3), ovarian cyst (1)
Group 3: Non-visualization of the appendix with other findings (3, 6.5%)	Ovarian torsion (1) Obstructive hydronephrosis (2)
Group 4: Probable acute appendicitis without other abnormal findings (9, 19.6%)	Acute appendicitis (8) Normal appendix (1)
Group 5: Probable acute appendicitis with other abnormal findings (2, 4.3%)	Non-surgical urinary disease: obstructive hydronephrosis (1) Non-surgical gynecologic disease: myoma red degeneration (1)
Group 6: Definite acute appendicitis (4, 8.7%)	Acute appendicitis (4)

Parameters	Surgical abdomen (n=13, 28.3%)	Non-surgical abdomen (n=33, 71.7%)	P value
Age	32.5 (30.5, 33.5)	30 (27, 34)	0.224
Gestational age (day)	112 (90, 193)	136.5 (96,185)	0.468
Trimester, n (%)			0.731
First	4 (33.3)	7 (20.6)
Second	6 (50.0)	21 (61.8)
Third	2 (16.7)	6 (17.6)
WBC (/mm³)	12,255 (10,600, 18,900)	10,420 (8,220, 13,100)	0.032
Neutrophil (%)	83.4 (77.6, 89.9)	77.4 (70.6, 81.8)	0.020
Lymphocyte (%)	10.4 (5.4, 14.7)	16.1 (12.1, 21.9)	0.010
NLR	8.2 (5.4, 16.9)	4.9 (3.2, 6.8)	0.013
Monocyte (%)	5.4 (3.7, 5.9)	5.3 (4.2, 7.2)	0.361
LMR	2.1 (1.5, 2.9)	3.0 (2.2, 4.4)	0.018
RDW (%)	13.3 (12.8, 13.7)	13.2 (12.8, 13.6)	0.950
Platelet (×10³/mm³)	233 (204.5, 251)	241.5 (217, 309)	0.260
PLR	184.8 (138.1, 235.3)	142.2 (109.2, 190.1)	0.133
CRP (mg/dL)	2.1 (0.5, 6.5)	0.5 (0.5, 0.6)	0.019
Total bilirubin (mg/dL)	0.74 (0.64, 0.80)	0.56 (0.32, 0.76)	0.025
AST (IU/L)	17 (13, 19)	17 (15, 21)	0.447
ALT (IU/L)	11 (10, 18)	13 (9, 17)	0.625
LDH (IU/L)	220 (175, 338)	272 (182.5, 341)	0.510
Urine pH	6.3 (6.0, 7.5)	6.5 (5.5, 7.0)	0.541
Pyuria, n (%)	0 (0)	5 (15.6)	0.301
Urine SG	1.015 (1.010, 1.020)	1.015 (1.010, 1.020)	0.314

Parameters	ROC area (0.95 CI)	Best cut-off value
WBC (/mm³)	0.710 (0.546, 0.873)	11,000
Neutrophil (%^a)	0.728 (0.553, 0.903)	79.9
Lymphocyte (%^b)	0.248 (0.077, 0.418)	19.6
NLR	0.744 (0.570, 0.918)	6.4
LMR	0.267 (0.110, 0.425)	2.6
CRP (mg/dL)	0.720 (0.53, 0.92)	1.82
Total bilirubin (mg/dL)	0.720 (0.57, 0.87)	0.66
PLR	0.647 (0.474, 0.820)	158.8

Cut-off value	Sensitivity (%)	Specificity (%)	Accuracy (%)	PPV (%)	NPV (%)	Odds ratio	P value
WBC≥11,000/mm³	75.0	61.8	65.2	40.9	87.5	4.85	0.028
Neutrophil≥79.9%^a	75.0	64.7	67.4	42.9	88.0	5.50	0.018
NLR≥6.4	66.7	70.6	69.6	44.4	85.7	4.80	0.023
CRP≥1.82 mg/dL	66.7	76.5	73.9	50.0	86.7	6.50	0.007
Total bilirubin≥0.66 mg/dL	75.0	61.8	65.2	40.9	87.5	4.85	0.028