Abstract
Objective
Anemia is observed in 30% of pregnancies with pyelonephritis, yet little is known
about the underlying etiology. Erythropoietin (EPO) is renally produced in response
to hypoxic and inflammatory conditions. Changes in serum EPO have been demonstrated
in infectious conditions in the nonpregnant population. EPO levels have been measured
in healthy pregnancy cohorts, but little is known about patterns in the setting of
renal inflammation. Our primary objective was to compare EPO levels in pregnant patients
at diagnosis of acute pyelonephritis to established trimester-specific norms. Secondary
objectives included assessing iron deficiency and hemolysis markers as alternate etiologies
of anemia.
Study Design
Prospective cohort study of pregnant people aged ≥ 18 years diagnosed with pyelonephritis,
defined as the presence of urinary tract infection symptoms plus flank pain, fever,
or nausea/vomiting. Blood samples including EPO, iron, transferrin, lactate dehydrogenase
(LDH), and haptoglobin were obtained within 72 hours of diagnosis. Demographics and
clinical data were abstracted from medical records. Wilcoxon Signed-Rank test compared
study EPO levels to noninfected pregnancy values established in the literature. Secondary
outcomes included number of patients with iron/hemolysis laboratories within trimester-specific
reference ranges.
Results
The study cohort included 17 patients with pyelonephritis in the second or third-trimester.
There were no eligible first-trimester patients during the study period. Anemia was
present on admission in 35.3% (6/17) of patients. EPO levels were significantly higher
in pyelonephritis patients during the second-trimester compared with literature-established
EPO levels in noninfected controls: 48.6 versus 10.6 mU/mL, (p = 0.0001). Secondary analysis demonstrated normal iron and haptoglobin levels in
most patients, and normal LDH in all patients.
Conclusion
EPO levels in pregnant pyelonephritis patients were significantly higher compared
with trimester-specific normative levels established in the literature. Evaluation
of iron and hemolysis studies showed inconsistent results but were often normal. This
pilot study may suggest a relationship between ineffective erythropoiesis and renal
inflammation in pregnancies complicated by pyelonephritis.
Key Points
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Anemia is present in 30 to 50% of pregnant patients with pyelonephritis.
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EPO was higher in the pyelonephritis cohort compared with normal pregnancy values.
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Iron and haptoglobin were normal in most patients, LDH was normal in all patients.
Keywords
anemia - erythropoietin - inflammation - pyelonephritis - urinary tract infection
- hemolysis
