(1) Background: Acute kidney injury (AKI) is a serious complication of hematopoietic stem cell transplantation (HSCT). (2) Methods: The aim was to identify the incidence, severity, and risk factors for AKI during the first 100 days after allo-HSCT; we performed a prospective observational study on 135 consecutive patients. (3) Results: The mean age was 38.3 ± 11.9 years (50.6% females), AKI developed in 93 patients (68.9%), the median time of appearance was 28 days, and the mean serum creatinine at the time of AKI was 1.8 ± 0.8 mg/dL. A total of 36 (38.7%) patients developed stage 1 AKI, 33 (35.5%) patients developed stage 2, and 24 (25.8%) patients developed stage 3; eight (8.6%) patients required temporary hemodialysis, and the mortality rate in these patients was 87.5%. Death was twice as frequent in the AKI subgroup, without statistical significance. Cyclosporine overdose (HR = 2.36, 95% CI: 1.45–3.85, p = 0.001), tacrolimus overdose (HR = 4.72, 95% CI: 2.22–10.01, p < 0.001), acute graft-versus-host disease (aGVHD) (HR = 1.96, 95% CI: 1.13–3.40, p = 0.01), and CRP level (HR = 1.009, 95% CI: 1.007–1.10, p < 0.001) were independent risk factors for AKI. Sepsis (HR = 5.37, 95% CI: 1.75–16.48, p = 0.003) and sinusoidal obstruction syndrome (HR = 5.10, 95% CI: 2.02–12.85, p = 0.001) were found as independent risk factors for AKI stage 3. (4) Conclusions: AKI occurs with high incidence and increased severity after allo-HSCT. Careful monitoring of calcineurin inhibitors and proper management of sepsis may reduce this risk.

Acute gastrointestinal graft-versus-host disease (GI aGVHD) is a significant and life-threatening complication in patients undergoing allogeneic stem cell transplantation (allo-SCT). Early diagnosis of GI aGVHD is crucial for improving patient outcomes, but it remains a challenge due to the condition’s nonspecific symptoms and the reliance on invasive diagnostic methods, such as biopsies and endoscopic procedures. In recent years, interest in non-invasive diagnostic techniques for graft-versus-host disease has increased, with contrast-enhanced ultrasound (CEUS) being one of them. For this reason, we aimed to examine the potential of ultrasound as a non-invasive, safe, and cost-effective alternative for the early detection and monitoring of GI aGVHD in this review. Our narrative review aims to describe the use of multimodal US that includes conventional US (B-mode and Doppler US) and advanced ultrasound techniques such as CEUS and CRTE for the non-invasive diagnosis of GI GVHD. We browsed several databases, including PubMed, Scopus, Web of Science, and Google Scholar. The search spanned 2000 to the present, focusing on articles written in English that reviewed the use of these imaging techniques in the context of GI GVHD. Following our research, we noticed that CEUS offers several advantages, including the real-time visualization of the gastrointestinal wall, assessment of blood flow, and detailed microvascular analysis—all achieved without the use of ionizing radiation. This feature makes CEUS an appealing option for repeated assessments, which are often necessary in monitoring the progression of GI aGVHD. When used in conjunction with conventional gastrointestinal ultrasound (GIUS), CEUS provides a more comprehensive view of the structural and functional changes occurring in the GI tract, potentially enhancing diagnostic accuracy and allowing for earlier intervention. In comparison to traditional diagnostic methods like tissue biopsy or CT scans, CEUS is less invasive, quicker to perform, and better tolerated by patients, especially those in fragile health following allo-SCT. Its non-invasive nature and ability to provide immediate imaging results make it a valuable tool for clinicians, particularly in settings where minimizing patient discomfort and risk is paramount. However, despite these advantages, there are still gaps in the literature regarding CEUS’s full diagnostic accuracy for GI aGVHD. Further research, including larger clinical trials and comparative studies, is needed to validate CEUS’s role in routine clinical practice and to establish standardized protocols for its use. Nonetheless, CEUS shows considerable potential to transform the diagnostic approach to GI aGVHD by improving early detection, reducing the need for invasive procedures, and ultimately enhancing treatment outcomes for affected patients.

Renal complications following hematopoietic stem cell transplantation (HSCT) pose substantial clinical challenges and impact patient outcomes. This chapter provides an in-depth analysis of the renal complications that may arise post-HSCT, including acute kidney injury (AKI), nephrotic syndrome, chronic kidney disease (CKD), and electrolyte imbalances. These complications occur from various factors such as nephrotoxic medications, graft-versus-host-disease (GVHD), infections, and pre-existing renal conditions. Early identification and management of renal dysfunction are crucial for optimizing patient care and prognosis. The chapter underscores the importance of vigilant monitoring, supportive measures, and timely interventions to mitigate renal complications post-HSCT. Enhanced understanding of these complications empowers clinicians to implement targeted preventive strategies and personalized therapeutic interventions, ultimately enhancing the overall outcomes and quality of life for HSCT recipients.

Intestinal microbiome dysbiosis has been associated with transplant-related mortality and graft-versus-host disease in allo-HSCT patients. We assessed how pre-transplant antibiotic and antineoplastic exposures, together with multidrug-resistant colonization, are associated with baseline gut microbiome diversity at allo-HSCT. We conducted a prospective, single-center cohort study at Fundeni Clinical Institute (Bucharest, Romania) between August 2024 and June 2025, enrolling 52 allo-HSCT recipients and 27 healthy controls. Fecal samples were collected before conditioning. Gut microbiome composition was assessed via 16S rRNA gene sequencing and analyzed using QIIME2 and R. Associations were evaluated using Wilcoxon test, multivariable linear regression, and PERMANOVA. Shannon diversity was significantly lower in patients (median 4.71, IQR 3.97–5.44) than in healthy controls (median 6.09, IQR 5.87–6.28; p < 0.001). In bivariate analyses, carbapenem (p adj = 0.02) and oxazolidinone exposure (p adj = 0.005) were associated with reduced diversity, while immunotherapy was associated with higher diversity (p adj = 0.042). Broad-spectrum penicillin (p adj = 0.062) and ESBL colonization (p adj = 0.066) did not reach significance. In the multivariable antibiotic model, although the overall model was statistically significant (model p = 0.039), no individual antibiotic class remained significantly associated with Shannon diversity after adjustment for co-exposures. Beta diversity differed modestly with carbapenem exposure (R² = 0.033, p = 0.019). Pre-transplant antibiotic exposures were associated with lower gut microbiome diversity at allo-HSCT admission, with patterns consistent with a cumulative rather than a class-specific association. These findings support antibiotic stewardship in pre-transplant care.

Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders driven mainly by somatic mutations in JAK2, CALR or MPL, but their clinical phenotype is also shaped by chronic inflammation, immune dysregulation, vascular complications and microenvironmental remodeling. Emerging evidence suggests that the gut microbiota may contribute to this inflammatory and immunometabolic landscape; however, the current literature remains heterogeneous and its translational relevance is still insufficiently defined. This critical narrative review maps the available evidence linking the gut microbiota, microbial metabolites and systemic microbial signatures to MPN biology. We distinguish direct human MPN data from indirect mechanistic evidence derived from studies of intestinal barrier dysfunction, thrombo-inflammation, hematopoietic regulation, allogeneic hematopoietic cell transplantation and infection risk. Across human MPN cohorts, the most consistent findings are not uniform changes in global microbial diversity, but rather alterations in specific immunoregulatory taxa, particularly reduced Firmicutes/Faecalibacterium-related communities and dysbiotic signatures associated with JAK2V617F status. Mechanistically, dysbiosis and impaired intestinal barrier integrity may facilitate low-grade endotoxemia, TLR4/NF-κB activation, cytokine amplification, endothelial activation and platelet priming. In parallel, microbial metabolites may influence hematopoietic stem cell programs, the bone marrow niche, megakaryopoiesis and thrombopoiesis. Treatment exposure and diet are relevant modifiers of the microbiota–inflammation axis, although available interventional data remain preliminary. Mendelian randomization and multi-omics studies provide hypothesis-generating evidence for microbiota–metabolome–MPN interactions, but require longitudinal validation, functional studies and contamination-aware analytical pipelines, especially for low-biomass blood and bone marrow samples. Microbiota-targeted strategies, including nutritional interventions and fecal or washed microbiota transplantation, represent promising but still investigational approaches, particularly in immunocompromised or post-transplant settings. Future studies should integrate microbiome, metabolome, genome, proteome, inflammatory biomarkers and clinical outcomes while controlling for diet, antibiotics, treatment exposure and driver mutation status. Such an approach may clarify whether the microbiota is a biomarker, mediator or therapeutic target in MPNs.

Introduction: Gastrointestinal graft-versus-host disease (GI GVHD) is a major complication of allogeneic haematopoietic stem-cell transplantation (allo-HSCT). Endoscopic biopsy with histopathological grading according to the Lerner system remains the diagnostic standard, although invasive sampling is frequently constrained in this fragile population. We assessed the relationship between a four-parameter contrast-enhanced ultrasound (CEUS) score and the Lerner histopathological grade. Methods: Prospective, single-centre study (October 2018 – December 2025). Adult allo-HSCT recipients with new-onset gastrointestinal symptoms underwent multimodal abdominal ultrasound, including CEUS with sulphur hexafluoride microbubbles, followed by endoscopic biopsy. A composite CEUS-GVHD score (range 0–12) integrated bowel-wall thickness, bowel-loop dilatation, contrast wash-out, and transmural microbubble migration. The cohort comprised 51 episodes (in 41 unique patients) with histopathologically confirmed GI GVHD and Lerner grade I–IV. A within-patient sensitivity analysis was performed on the first chronologically documented episode per patient (n=41), and additional sensitivity analyses were performed by stratification according to concurrent gastrointestinal infection and according to GVHD form (acute vs chronic). Results: The total CEUS-GVHD score showed a positive correlation with the Lerner grade (p < 0.001). Median CEUS scores across grades were 5.5 (Lerner I), 7 (II), 8.5 (III), and 10 (IV) (p < 0.001). Among individual parameters, transmural microbubble migration showed the highest correlation, followed by bowel-wall thickness and contrast wash-out; these three correlations remained significant after Bonferroni correction. The bowel-loop dilatation correlation did not retain significance after correction. In an exploratory analysis, the area under the ROC curve of the total CEUS-GVHD score for discriminating severe (Lerner III–IV) from mild (Lerner I–II) histopathological GI GVHD was 0.853, with the same point estimate retained in the within-patient sensitivity analysis (AUC 0.853). Conclusion: In this single-centre cohort of biopsy-confirmed GI GVHD, the CEUS-GVHD score showed a moderate-to-strong association with Lerner histopathological grade. Because the study included only confirmed GI GVHD episodes, these findings support CEUS as a potential adjunct for severity assessment, not as a replacement for diagnostic biopsy. External multicentre validation with multiple operators is required.