Effects of altitude on spleen volume: sonographic assessment

Discrepancies in Splenic Size Measurement: A Comparative Analysis of Ultrasound and Computed Tomography

The accurate measurement of splenic size is essential for the diagnosis and management of various gastrointestinal and hematological conditions. While ultrasound (US) and computed tomography (CT) are widely used imaging modalities for assessing splenic size, discrepancies between their measurements have been observed in clinical practice. This study aimed to analyze the measurement differences between US and CT and identify factors influencing these differences. A retrospective analysis of 598 asymptomatic patients who underwent both abdominal US and CT was conducted. Measurements of splenic size obtained from US, axial CT, and coronal CT scans were compared, and various factors such as patient demographics, operator experience, and imaging parameters were evaluated to elucidate their impact on the measurement discrepancies. The results revealed that US consistently underestimated splenic size compared to CT. The magnitude of the discrepancy was influenced by factors such as patient age, body mass index (BMI), depth of the spleen from skin on US and that on CT, visibility of the splenic hilum on US, sonic window quality, and operator experience. This study underscores the importance of considering these factors when interpreting splenic measurements obtained from different imaging modalities in clinical practice.

Eight weeks of dry dynamic breath-hold training results in larger spleen volume but does not increase haemoglobin concentration

Purpose: It has previously been reported that repeated exposure to hypoxia increases spleen size and haemoglobin (HGB) level and recent reports on the effect apnoea has on spleen size and haematological parameters are contradictory. Therefore, this study aims to evaluate the effect apnoea training has on spleen size and haematological parameters.

Methods: The breath-holding (BH) group was comprised of 12 local student-athletes with no BH exercise experience who performed BH jogging and BH jumping rope dynamic apnoea protocols, five times weekly for 8 weeks. The BH event duration was progressively increased as the apnoea tolerance of the athletes improved (20 to 35 s). The same training task was performed by the control group (n = 10) without BH. Spleen sizes were measured with an ultrasound system and a complete blood cell analysis was performed on the median cubital venous blood.

Results: Spleen volume in the BH group increased from 109 ± 13 ml to 136 ± 13 ml (p < 0.001), and bulky platelets decreased from 70.50 ± 5.83 to 65.17 ± 5.87 (p = 0.034), but no changes were recorded for erythrocytes (p = 0.914), HGB (p = 0.637), PLTs (p = 0.346) and WBC (p = 0.532). No changes were recorded for the control group regarding spleen size or haematological parameters.

Conclusion: Eight weeks of dry dynamic apnoea training increased spleen size and decreased the number of circulating bulky platelets in the athletes who were assessed in this study. However, the baseline RBC counts and HGB levels of the athletes were not altered by the training programme.

Methods of Ultrasound Spleen Morphometry

This article presents a review of the methods of determining spleen size in sonography, computed tomography, and magnetic resonance imaging. The review aims to summarize the data on the methods of estimating the linear dimensions of the spleen and splenic volume and describe the physiological variability of spleen size depending on sex, age, and different physiological conditions. We systematized the methods used for measuring the spleen and presented them in the form of a table, analyzed the results of previous studies, and compared the accuracy of different methods of calculating the splenic volume using a variety of diagnostic methods.

Morphometric assessment of spleen dimensions and its determinants among individuals living in Arba Minch town, southern Ethiopia

Introduction

The spleen is a vital lymphoid soft organ that demands constant attention from the clinical point of view. It is a multi-dimensional organ that enlarges in its all dimensions during some disease condition. The detection of the spleen by palpation is not an indicator of an enlarged spleen because normal spleen may be palpable. Therefore, this study aimed to assess the morphometry of spleen dimensions and its determinants among individuals living in Arba Minch town by sonographic examinations.

Methods and materials

Community-based cross-sectional study was conducted in Arba Minch town from February 1 to March 30, 2020. Seven hundred and eight study participants were selected using a multi-stage systematic random sampling technique. Data were checked for completeness, edited, coded and entered into Epi-Data version 3.1 and exported to STATA software version 16 for analysis.

Result

The mean splenic length, width, thickness and volume were 10.24 cm, 4.79 cm, 3.93 cm, and 109.34 cm³, respectively. The mean spleen length, width, thickness and volumes among males were 10.64 cm, 4.92 cm, 4.05 cm and 119.81 cm³ and among females were 9.75 cm, 4.63 cm, 3.78 cm and 96.50 cm³ respectively. As age increased by one year the mean spleen length, width, thickness and volume was decreased by 0.032 cm, 0.018 cm 0.004 cm and 0.012 cm respectively. As height increased by 1 cm the mean spleen width and volume were increased by 0.096 cm and 0.052 cm respectively. As we go from male to female the mean spleen length decreased by 0.294 cm.

Conclusion

The spleen dimensions were higher in males than females. Splenic length was determined by age & sex, the spleen width was determined by age & height, the spleen volume was determined by age & height and the spleen thickness was determined by age.

Spleen Contraction During Sudden Eupneic Hypoxia Elevates Hemoglobin Concentration

The spleen contracts progressively during moderate normobaric hypoxia exposure of 20 min, which elevates hemoglobin concentration (Hb). However, acute hypoxia exposure could be shorter and more severe when oxygen systems fail during, e.g., high-altitude sky diving, aircraft cabin pressure drop, balloon flights, extreme altitude climbing, and in some maladies. We aimed to evaluate the speed and magnitude of spleen contraction during short exposure to extreme eupneic hypoxia and its subsequent recovery on oxygen. Eight female and seven male volunteers were exposed to normobaric hypoxia (10% oxygen) for 10 min during sitting rest, followed by 10 min on 100% oxygen. Heart rate (HR), arterial oxygen saturation (SpO₂), and mean arterial blood pressure (MAP) were measured continuously. The spleen was measured via ultrasonic imaging every minute for volume calculations, and venous blood samples were drawn before and after exposure for hemoglobin concentration (Hb). Mean (SD) spleen volume was 279 (115) mL before exposure, 219 (75) mL (21% reduction; P = 0.005) at 3 min of exposure, and 201 (93) mL after 10 min exposure to hypoxia (28% reduction; P < 0.001). Hb was 138.8 (7.6) g·L⁻¹ before and 142.9 (8.1) g·L⁻¹ after 10 min of exposure (2.9% increase; P < 0.001). SpO₂ was 96.4 (1.7)% before exposure and 74.7 (8.4)% during the last minute of exposure (22.5% reduction; P < 0.001). HR increased from 80 (14) to 90 (17) bpm during exposure (12% increase, P < 0.05). MAP remained unchanged. After 10 min recovery on oxygen, values had been restored for spleen volume and Hb, while SpO₂ was higher and HR lower compared with before hypoxia exposure. We concluded that acute normobaric hypoxia of only 10 min caused significant spleen volume contraction with Hb increase. This rapid spleen response, evident already after 3 min of exposure, could have a protective effect during sudden exposure to severe hypoxia.

Exposure to hypoxia causes stress erythropoiesis and downregulates immune response genes in spleen of mice

BACKGROUND

The spleen is the largest secondary lymphoid organ and the main site where stress erythropoiesis occurs. It is known that hypoxia triggers the expansion of erythroid progenitors; however, its effects on splenic gene expression are still unclear. Here, we examined splenic global gene expression patterns by time-series RNA-seq after exposing mice to hypoxia for 0, 1, 3, 5, 7 and 13 days.

RESULTS

Morphological analysis showed that on the 3rd day there was a significant increase in the spleen index and in the proliferation of erythroid progenitors. RNA-sequencing analysis revealed that the overall expression of genes decreased with increased hypoxic exposure. Compared with the control group, 1380, 3430, 4396, 3026, and 1636 genes were differentially expressed on days 1, 3, 5, 7 and 13, respectively. Clustering analysis of the intersection of differentially expressed genes pointed to 739 genes, 628 of which were upregulated, and GO analysis revealed a significant enrichment for cell proliferation. Enriched GO terms of downregulated genes were associated with immune cell activation. Expression of Gata1, Tal1 and Klf1 was significantly altered during stress erythropoiesis. Furthermore, expression of genes involved in the immune response was inhibited, and NK cells decreased.

CONCLUSIONS

The spleen of mice conquer hypoxia exposure in two ways. Stress erythropoiesis regulated by three transcription factors and genes in immune response were downregulated. These findings expand our knowledge of splenic transcriptional changes during hypoxia.

Spleen Volume and Contraction During Apnea in Mt. Everest Climbers and Everest Base Camp Trekkers

The human spleen can contract and transiently boost the blood with stored erythrocytes. We measured spleen volume and contraction during apneas in two groups, each containing 12 Caucasian participants (each 3 women): one group planning to summit Mt. Everest (8848 m; "Climbers") and another trekking to Everest Base Camp (5300 m; "Trekkers"). Tests were done in Kathmandu (1370 m) 1-3 days after arrival, before the Climb/Trek. Age, height, weight, vital capacity, resting heart rate, and arterial oxygen saturation were similar between groups (not significant). After 15 minutes of sitting rest, all participants performed a 1-minute apnea and, after 2 minutes of rest, 1 maximal duration apnea was performed. Six of the climbers did a third apnea and hemoglobin concentration (Hb) was measured. Three axial spleen diameters were measured by ultrasonic imaging before and after the apneas for spleen volume calculation. Mean (standard deviation) baseline spleen volume was larger in Climbers [367 (181) mL] than in Trekkers [228 (70) mL; p = 0.022]. Spleen contraction occurred during apneas in both groups, with about twice the magnitude in Climbers. Three apneas in six of the Climbers resulted in a spleen volume reduction from 348 (145) to 202 (91) mL (p = 0.005) and an Hb elevation from 147.9 (13.1) to 153.3 (11.3) g/L (p = 0.024). Maximal apneic duration was longer in Climbers [88 (23) seconds vs. 67 (18) seconds in Trekkers; p = 0.023]. We concluded that a large spleen characterizes Climbers, suggesting that spleen function may be important for high-altitude climbing performance.

Spleen contraction elevates hemoglobin concentration at high altitude during rest and exercise

PURPOSE

Hypoxia and exercise are known to separately trigger spleen contraction, leading to release of stored erythrocytes. We studied spleen volume and hemoglobin concentration (Hb) during rest and exercise at three altitudes.

METHODS

Eleven healthy lowlanders did a 5-min modified Harvard step test at 1370, 3700 and 4200 m altitude. Spleen volume was measured via ultrasonic imaging and capillary Hb with Hemocue during rest and after the step test, and arterial oxygen saturation (SaO₂), heart rate (HR), expiratory CO₂ (ETCO₂) and respiratory rate (RR) across the test.

RESULTS

Resting spleen volume was reduced with increasing altitude and further reduced with exercise at all altitudes. Mean (SE) baseline spleen volume at 1370 m was 252 (20) mL and after exercise, it was 199 (15) mL (P < 0.01). At 3700 m, baseline spleen volume was 231 (22) mL and after exercise 166 (12) mL (P < 0.05). At 4200 m baseline volume was 210 (23) mL and after exercise 172 (20) mL (P < 0.05). After 10 min, spleen volume increased to baseline at all altitudes (NS). Baseline Hb increased with altitude from 138.9 (6.1) g/L at 1370 m, to 141.2 (4.1) at 3700 m and 152.4 (4.0) at 4200 m (P < 0.01). At all altitudes Hb increased from baseline during exercise to 146.8 (5.7) g/L at 1370 m, 150.4 (3.8) g/L at 3700 m and 157.3 (3.8) g/L at 4200 m (all P < 0.05 from baseline). Hb had returned to baseline after 10 min rest at all altitudes (NS). The spleen-derived Hb elevation during exercise was smaller at 4200 m compared to 3700 m (P < 0.05). Cardiorespiratory variables were also affected by altitude during both rest and exercise.

CONCLUSIONS

The spleen contracts and mobilizes stored red blood cells during rest at high altitude and contracts further during exercise, to increase oxygen delivery to tissues during acute hypoxia. The attenuated Hb response to exercise at the highest altitude is likely due to the greater recruitment of the spleen reserve during rest, and that maximal spleen contraction is reached with exercise.

Spleen reactivity during incremental ascent to altitude

The spleen contains a reservoir of red blood cells that are mobilized into circulation when under physiological stress. Despite the spleen having an established role in compensation to acute hypoxia, no previous work has assessed the role of the spleen during ascent to high altitude. Twelve participants completed 2 min of handgrip exercise at 30% of maximal voluntary contraction at 1,045, 3,440, and 4,240 m. In a subset of eight participants, an infusion of phenylephrine hydrochloride was administered at a dosage of 30 µg/l of predicted blood volume at each altitude. The spleen was imaged by ultrasound via a 2- to 5.5-MHz curvilinear probe. Spleen volume was calculated by the prolate ellipsoid formula. Finger capillary blood samples were taken to measure hematocrit. Spleen images and hematocrit were taken both before and at the end of both handgrip and phenylephrine infusion. No changes in resting spleen volume were observed between altitudes. At low altitude, the spleen contracted in response to handgrip [272.8 ml (SD 102.3) vs. 249.6 ml (SD 105.7), P = 0.009], leading to an increase in hematocrit (42.6% (SD 3.3) vs. 44.3% (SD 3.3), P = 0.023] but did not contract or increase hematocrit at the high-altitude locations. Infusion of phenylephrine led to spleen contraction at all altitudes, but only lead to an increase in hematocrit at low altitude. These data reveal that the human spleen may not contribute to acclimatization to chronic hypoxia, contrary to its response to acute sympathoexcitation. These results are explained by alterations in spleen reactivity to increased sympathetic activation at altitude. NEW & NOTEWORTHY The present study demonstrated that, despite the known role of the human spleen in increasing oxygen delivery to tissues during acute hypoxia scenarios, the spleen does not mobilize red blood cells during ascent to high altitude. Furthermore, the spleen's response to acute stressors at altitude depends on the nature of the stressor; the spleen's sensitivity to neurotransmitter is maintained, while its reflex response to stress is dampened.

Sonographic assessment of spleen size in Turkish migrants with Familial Mediterranean fever in Germany

OBJECTIVES

Familial Mediterranean fever (FMF) can be associated with splenomegaly. Prospective quantitative data are lacking. We performed a sonographic assessment of spleen size in patients with FMF and healthy control participants to assess its diagnostic value.

METHODS

Patients with FMF according to the criteria of Livneh et al (Arthritis Rheum 1997; 40:1879-1885) who were in an asymptomatic interval and control participants were prospectively included in this study in Germany and underwent sonographic measurement of the spleen as well as a structured interview and a physical examination. Patients and controls were Turkish migrants.

RESULTS

Thirty-six patients and 27 controls were included. Patients and controls did not differ significantly in age (mean ± SD, 34.8 ± 9.7 versus 33.3 ± 10.0 years, respectively; P = .56), sex, height, weight, or body mass index (26.7 ± 4.7 versus 26.1 ± 4.3 kg/m(2); P = .63). Spleen size was greater in patients than controls in width (4.3 ± 1.0 versus 3.7 ± 0.7 cm; P = .008) and also length (12.1 ± 1.9 versus 10.5 ± 1.4 cm; P = .001). Twenty-six of 36 patients (72.2%) had a history of appendectomy compared to 3 of 27 controls (11.1%; P < .001). The combination of an enlarged spleen (length >11 cm and/or width >4 cm) gave specificity of 100% (95% confidence interval, 87%-100%) and a positive predictive value of 100% (95% confidence interval, 78%-100%) for the diagnosis of FMF in our study.

CONCLUSIONS

Spleen size as evaluated by sonography is larger in patients with FMF compared to healthy controls. Most patients with FMF included in this study had undergone appendectomy. Familial Mediterranean fever should be considered as a differential diagnosis in Turkish migrants in Germany if the spleen is enlarged and a history of appendectomy is reported.

Short-term effects of normobaric hypoxia on the human spleen

Spleen contraction resulting in an increase in circulating erythrocytes has been shown to occur during apnea. This effect, however, has not previously been studied during normobaric hypoxia whilst breathing. After 20 min of horizontal rest and normoxic breathing, five subjects underwent 20-min of normobaric hypoxic breathing (12.8% oxygen) followed by 10 min of normoxic breathing. Ultrasound measurements of spleen volume and samples for venous hemoglobin concentration (Hb) and hematocrit (Hct) were taken simultaneously at short intervals from 20 min before until 10 min after the hypoxic period. Heart rate, arterial oxygen saturation (SaO(2)) and respiration rate were recorded continuously. During hypoxia, a reduction in SaO(2) by 34% (P < 0.01) was accompanied by an 18% reduction in spleen volume and a 2.1% increase in both Hb and Hct (P < 0.05). Heart rate increased 28% above baseline (P < 0.05). Within 3 min after hypoxia SaO(2) had returned to pre-hypoxic levels, and spleen volume, Hb and Hct had all returned to pre-hypoxic levels within 10 min. Respiratory rate remained stable throughout the protocol. This study of short-term exposure to eupneic normobaric hypoxia suggests that hypoxia plays a key role in triggering spleen contraction and subsequent release of stored erythrocytes in humans. This response could be beneficial during early altitude acclimatization.