Erschienen in:
24.04.2021 | Art in the Ward
Unexplained life-threatening high anion gap metabolic acidosis: the answer is in the urine!
Erschienen in: Journal of Nephrology | Ausgabe 6/2021
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A 49-year-old black male was referred to the Emergency Department (ED) after a 24-h history of confusion, progressive blurring of vision and altered mental status. On admission, the patient was confused and showed slurred speech and dyspnea. A history of alcohol abuse, and recent use of non-specified “energy drinks” was reported. The patient was apyretic; blood pressure was 170/80 mmHg, pulse rate 98 beats/min, respiratory rate 38 breaths/min, and peripheral oxygen saturation 99% at room air. Physical examination was unremarkable, but he showed progressive depression of cognitive status with no motor deficits nor nuchal rigidity. Brain CT scan was negative. Arterial blood gas showed high anion gap metabolic acidosis with slightly increased lactate levels (Table 1). Measured osmolality was 301 mOsm/kg, with no evident osmolal gap. Laboratory workup revealed stage 3 oliguric Acute Kidney Injury (AKI) with hyperkalemia (Table 1). Routine toxicology screen was negative. Automated urinalysis indicated abundant urate crystals, however, the evaluation of urine sediment under polarized light showed the massive presence of needle-shaped, birefringent crystals consisting of calcium oxalate monohydrate, as confirmed by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) and X-ray Diffraction (XRD) (Fig. 1).
Table 1
Laboratory data at Emergency Department admission, before and after 16-h SLED session
|
Laboratory data
|
ED admission
|
1 h later
|
SLED start
|
SLED, 16-h
|
12-h after SLED end
|
|---|---|---|---|---|---|
|
Blood glucose, mg/dL
|
101
|
144
|
205
|
–
|
99
|
|
SUN, mg/dL
|
25
|
–
|
37
|
–
|
33
|
|
SCr, mg/dL
|
2.3
|
–
|
4.1
|
–
|
5
|
|
Sodium, mmol/L
|
139
|
141
|
139
|
–
|
140
|
|
Potassium, mmol/L
|
6.6
|
6.7
|
7
|
–
|
4.3
|
|
Chloride, mmol/l
|
114
|
113
|
101
|
–
|
102
|
|
Calcium, mg/dL
|
–
|
–
|
7.4
|
–
|
8.6
|
|
Hb, g/dL
|
16.2
|
14.6
|
14.3
|
–
|
11.6
|
|
Platelet count, × 103/μL
|
216
|
–
|
203
|
–
|
127
|
|
White blood cell count, × 103/μL
|
10.61
|
–
|
21
|
–
|
14.5
|
|
LDH, IU/L
|
288
|
–
|
331
|
–
|
472
|
|
AST, IU/L
|
41
|
–
|
37
|
–
|
32
|
|
ALT, IU/L
|
45
|
–
|
41
|
–
|
75
|
|
INR
|
1.21
|
–
|
1.40
|
–
|
1.45
|
|
pH
|
7.24
|
7.27
|
7.26
|
–
|
7.47
|
|
pO2, mmHg
|
135
|
134
|
123
|
–
|
86
|
|
pCO2, mmHg
|
9
|
13.3
|
12.5
|
–
|
34.9
|
|
Ionized calcium, mmol/L
|
1.13
|
1.00
|
0.96
|
0.99
|
1.00
|
|
Bicarbonate, mmol/L
|
3.8
|
5.9
|
7.1
|
19.6
|
25.7
|
|
Lactate, mmol/L
|
2.2
|
5.2
|
4.9
|
–
|
0.9
|
|
Anion Gap, mmol/L
|
22.1
|
22.2
|
30.7
|
–
|
12.3
|
|
Calculated osmolality, mOsm/Kg
|
293
|
–
|
–
|
–
|
–
|
|
Measured osmolality, mOsm/Kg
|
301
|
–
|
–
|
–
|
–
|
|
Ethanol, g/l
|
< 0.03
|
–
|
–
|
–
|
–
|
|
Serum ethylene glycol, mg/dL
|
12.0
|
–
|
–
|
< 2.5
|
–
|
|
Urinary ethylene glycol, mg/dL
|
93.7
|
–
|
–
|
–
|
–
|
Fig. 1
Urinary sediment examination and analysis of crystals. Urinary sediment (a, × 400) shows abundant erythrocytes and needle crystals, sometimes aggregated in bundles, birefringent under polarized light (b, × 400). As shown in the bottom panel characterization of urinary crystals was performed. Scanning Electron Microscopy (SEM) investigation, performed at 2, 5, 10 and 20 kV of electronic acceleration voltage through SEM–FIB Zeiss Auriga Compact, shows bundles of elongated and flat six-sided (“picket fences”) crystals (c); Energy Dispersive X-ray (EDX, panel d) analysis revealed a relative composition of Ca (12%), C (24%) and O (48 + 4%) which unambiguously matches the elemental ratio expected for hydrated CaC2O4. In addition, about 10% of NaCl and 1% of KCl are detected as spurious phases. Measured X-ray diffraction (XRD) (e, black line) shows a diffraction pattern consistent with calcium oxalate monohydrate (blue line) with a small component of calcium oxalate dihydrate (red line). X-Ray diffraction measurements were performed using a Rigaku Smartlab XE diffractometer with Cu Kα radiation. The beam was parallelized by using the CBO optic device and 5.0° soller slits were used both on the incident and diffracted beam. The sample was placed on a zero background sample holder and the HyPix 3000 detector was operated in 1D mode, collecting in the 10–60° 2θ range with 0.05° step size and 1°/min speed
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