Contrast-enhanced ultrasound performed under urgent conditions. Indications, review of the technique, clinical examples and limitations

Ovarian torsion: incremental role of contrast-enhanced ultrasound

We highlight the role of contrast-enhanced ultrasound (CEUS) as a supplementary modality to ultrasound (USG) examination in ovarian torsion in this case report. The reported patient had clinical history suspicious of ovarian torsion; however, USG and Doppler flow study findings were equivocal. CEUS was performed to solve the diagnostic dilemma and to know the status of ovarian parenchymal viability which revealed non-enhancement of the ovarian cyst wall and pedicle throughout the USG examination thus establishing the diagnosis of non-viable or infarcted ovarian parenchyma. The per operative and histopathology findings were consistent with our CEUS findings. CEUS is an emerging promising modality which provides information regarding parenchymal perfusion, resulting in a reliable diagnosis of ovarian torsion along with information on ovarian parenchymal viability. This ability makes CEUS equivalent to contrast-enhanced CT or MRI.

Paradoxical Pulmonary Embolism in a Patient with Bilateral Renal Infarction: The Role of Contrast-enhanced Ultrasound Imaging

We present the case of a 52-year-old male who was admitted to the hospital for a bilateral pulmonary embolism. On the 5th day of hospitalization, an acute kidney injury (AKI) occurred. A transesophageal echocardiogram was performed and it demonstrated a large patent foramen ovale with a consistent right-to-left shunt. Contrast-enhanced ultrasound (CEUS) was performed and it demonstrated multiple bilateral renal ischemic areas. CEUS represents a valid alternative to computed tomography or magnetic resonance to confirm the diagnosis of bilateral kidney infarction, especially in patients who experience an AKI.

The Technique and Advantages of Contrast-Enhanced Ultrasound in the Diagnosis and Follow-Up of Traumatic Abdomen Solid Organ Injuries

Trauma is one of the most common causes of death or permanent disability in young people, so a timely diagnostic approach is crucial. In polytrauma patients, CEUS (contrast enhanced ultrasound) has been shown to be more sensitive than US (ultrasound) for the detection of solid organ injuries, improving the identification and grading of traumatic abdominal lesions with levels of sensitivity and specificity similar to those seen with MDCT (multidetector tomography). CEUS is recommended for the diagnostic evaluation of hemodynamically stable patients with isolated blunt moderate-energy abdominal traumas and the diagnostic follow-up of conservatively managed abdominal traumas. In this pictorial review, we illustrate the advantages and disadvantages of CEUS and the procedure details with tips and tricks during the investigation of blunt moderate-energy abdominal trauma as well as during follow-up in non-operative management.

Recent advances in vascular ultrasound imaging technology and their clinical implications

In this paper recent advances in vascular ultrasound imaging technology are discussed, including three-dimensional ultrasound (3DUS), contrast-enhanced ultrasound (CEUS) and strain- (SE) and shear-wave-elastography (SWE). 3DUS imaging allows visualisation of the actual 3D anatomy and more recently of flow, and assessment of geometrical, morphological and mechanical features in the carotid artery and the aorta. CEUS involves the use of microbubble contrast agents to estimate sensitive blood flow and neovascularisation (formation of new microvessels). Recent developments include the implementation of computerised tools for automated analysis and quantification of CEUS images, and the possibility to measure blood flow velocity in the aorta. SE, which yields anatomical maps of tissue strain, is increasingly being used to investigate the vulnerability of the carotid plaque, but is also promising for the coronary artery and the aorta. SWE relies on the generation of a shear wave by remote acoustic palpation and its acquisition by ultrafast imaging, and is useful for measuring arterial stiffness. Such advances in vascular ultrasound technology, with appropriate validation in clinical trials, could positively change current management of patients with vascular disease, and improve stratification of cardiovascular risk.

Contrast enhanced ultrasound versus multiphasic contrast enhanced computed tomography in evaluation of gallbladder lesions

AIM

To compare the diagnostic performance of contrast enhanced ultrasound (CEUS) and multiphasic contrast enhanced computed tomography (CECT) in differentiating benign and malignant gallbladder (GB) lesions.

METHODS

This prospective ethical review board approved study comprised consecutive patients with GB lesions who underwent CEUS and multiphasic CECT at a tertiary care referral center. The enhancement patterns at CEUS and CT were compared. The quantitative CEUS parameters including arrival time (AT), AT in liver, time to peak enhancement, and washout time (WT) were assessed. The diagnostic performance of CEUS and CT features was calculated using receiver operating characteristic analysis. A subgroup analysis was performed for patients with GB wall thickening. Multivariate analysis was performed to identify features significantly associated with malignancy.

RESULTS

Over the study period, 30 patients (mean age, 52.8 ± 12.2 years, 17 females) with GB lesions were evaluated. Benign and malignant diseases were present in 13 and 17 patients, respectively. There was excellent agreement between CEUS and CT findings. Among the quantitative CEUS features, only WT was significantly associated with malignancy in the overall group (p < 0.001) and wall thickening subgroup (p = 0.007). WT within 53.5 s and 51.5 s had sensitivity of 88.2% and 81.8% and specificity of 84.5% and 100% in diagnosing malignant lesions in the overall group (AUC 0.900) and the wall thickening subgroup (area under curve, AUC 0.927), respectively. At multivariate analysis, features that were significantly associated with malignant lesions in the overall group were disruption of GB wall (CEUS), intralesional non-enhancing areas (CEUS), liver involvement (CEUS or CT), and arterial phase hyperenhancement (CT) in the overall group and disruption of GB wall (CEUS), WT (CEUS), and liver involvement (CEUS or CT) in the wall thickening subgroup.

CONCLUSION

CEUS is a useful adjunct to CT in evaluation of GB lesions. Its utilization in patients with GB wall thickening may improve detection of malignancy.

Is contrast-enhanced ultrasonography (CEUS) useful in the assessment of obstructive uropathy-induced perfusion disorders?

Aim: The study aimed to evaluate the usefulness of contrast-enhanced ultrasonography in renal perfusion disorders caused by obstructive uropathy. Case description: We present a case of a patient with a horseshoe kidney, in which the urine outflow from the right part of the kidney was blocked due to the presence of a bladder tumour infiltrating the ureter. Perfusion disorders in both parts of the kidney, visible in computed tomography, were partially reflected in the ultrasound image. Conclusions: Doppler ultrasound and contrast-enhanced ultrasound may be useful for monitoring perfusion disorders in the course of obstructive uropathy, provided that appropriate methodology is developed to compare blood flow in both kidneys.

A pictorial review of the utility of CEUS in thoracic biopsies

Lung cancer is one of the commonest malignancies worldwide and necessitates both early and personalised treatment. A key requirement is histological sampling with immunohistochemistry obtained usually from percutaneous biopsy. Conventionally thoracic biopsies are performed using CT guidance, but more recently, there has been development of physician led ultrasound biopsy for pleural lesions. Contrast-enhanced ultrasound (CEUS) has been increasingly used in interventional procedures and is able to offer benefits for thoracic biopsies including improving lesional visualisation and characterisation, targeting viable tissue and avoiding critical vascular structures as well as evaluating for the presence of post-procedural complications. This educational review aims to benefits of the role of CEUS in thoracic biopsies.

Sonography of the penis/erectile dysfunction

Erectile dysfunction (ED) is defined as the persistent inability to achieve and/or maintain an erection for a satisfactory sexual activity. It is secondary to several organic, psychogenic, and combined causes, and represents a serious health dilemma affecting both men and their partners. The diagnostic approach to erectile dysfunction has significantly changed in the last years with the advent of phosphodiesterase-5 (PDE5) inhibitors, and with the recognition that surgical treatment of both arterial insufficiency and penile venous leak have poor long-term clinical outcomes. Although imaging modalities have diminished in importance, differentiating among causes of erectile dysfunction remains mandatory in good medical practice, and ultrasound (US) still remains the cornerstone of the diagnostic workup. US provides an objective, minimally invasive evaluation of penile hemodynamics. Moreover, it provides an excellent depiction of the penile anatomy and of its changes in pathological conditions such as in patients with Peyronie's disease, priapism, and posttraumatic erectile dysfunction.

Complete testicular infarction secondary to epididymoorchitis and pyocele

Epididymoorchitis is a relatively common urologic condition involving the scrotum which presents with unilateral pain and swelling. It is typically treated with antibiotics but can progress to complications such as scrotal pyocele. Global testicular infarction is an exceedingly rare but devastating complication of epididymoorchitis. Grey scale and color Doppler ultrasound demonstrate testicular hypovascularity with subsequent hypoechoic changes of the testicular parenchyma. Scrotal MRI shows T2 hyperintense changes through the testicle with nonenhancement of the testicular parenchyma post contrast, consistent with infarction. The cause of global infarction in epididymitis is uncertain but may be due to mixed arterial and venous insufficiency. This case illustrates a 41-year-old male that developed acute left testicular pain. Initial ultrasound showed an enlarged left testicle with hyperemia. The patient's symptoms progressed and a scrotal MRI demonstrated a lack of left testicular enhancement consistent with global infarction, as well as an adjacent pyocele.

Safety and efficacy of percutaneous microwave ablation for post-procedural haemostasis: a bi-central retrospective study focusing on safety and efficacy

OBJECTIVE

To review safety and efficacy of percutaneous microwave ablation (MWA) for post-procedural haemostasis.

METHODS

Institutional databases retrospective research identified 10 cases of iatrogenic bleeding who underwent percutaneous MWA for post-procedural haemostasis. Ultrasound examination with Doppler and contrast enhancement identified a source of active bleeding prior to ablation; additionally they were used as guiding modality for antenna insertion whilst, post-ablation, assessed the lack of active extravasation. Target locations included liver intercostal space spleen and thyroid gland. Technical success was defined as positioning of the antenna on the desired location. Treatment end point was considered the disappearance of active extravasation in both Doppler imaging and contrast-enhanced ultrasound.

RESULTS

Technical success (i.e. positioning of the antenna on the desired location) was achieved in all cases. No complications were noted. All patients post MWA remained haemodynamically stable with no need for transfusion and were discharged from the hospital the next morning. Imaging and clinical follow-up in all patients before exiting the hospital did not depict any sign of active extravasation or bleeding.

CONCLUSION

Our limited experience reports preliminary data showing that MWA could be added in the armamentarium of percutaneous therapies for iatrogenic bleeding. More prospective studies with larger patient samples are necessary for verification of this technique as well as for drawing broader conclusions in order to evaluate the place of percutaneous ablation in the treatment algorithm of haemorrhage.

ADVANCES IN KNOWLEDGE

Percutaneous ablation might have a role in haemostasis in well-selected cases.

Contrast-Enhanced Ultrasound Guidance for Interventional Procedures

Since its introduction, contrast-enhanced ultrasound (CEUS) has gained an important role in the diagnosis and management of abdominal and pelvic diseases. Contrast-enhanced ultrasound can improve lesion detection rates as well as success rates of interventional procedures when compared to conventional ultrasound alone. Additionally, CEUS enables the interventionalist to assess the dynamic enhancement of different tissues and lesions, without the adverse effects of contrast-enhanced computed tomography, such as exposure to ionizing radiation and nephrotoxicity from iodinated contrast material. This review article describes the various applications and advantages of the use of CEUS to enhance performance of ultrasound-guided interventions in the abdomen and pelvis.

Diagnostic value of contrast-enhanced ultrasound (CEUS) and comparison with color Doppler ultrasound and magnetic resonance in a case of scrotal trauma

Intratesticular hematoma is one of the most frequent presentations of scrotal trauma. Ultrasound is the first-line imaging modality in the evaluation of scrotal trauma, and its findings are crucial for the choice of treatment. An intratesticular hematoma may represent a diagnostic pitfall for the investigating physician since its appearance may mimic other conditions, such as testicular neoplasms or segmental infarction. Although the gold standard imaging modality for the characterization of a testicular lesion is contrast-enhanced magnetic resonance (MR), MR equipment is not always available in an emergency department. Contrast-enhanced ultrasound (CEUS) may represent a valid and cheaper alternative compared with MR, which may aid the physician in the differential diagnosis. We describe the case of a 19-year-old male with a scrotal trauma following a motorcycle crash. In accordance with the literature, we carried out a contrast-medium whole-body computed tomography for the evaluation of any potential traumatic injury. Because of scrotal swelling and the patient complaining about pain in the right testicle, we performed a scrotal ultrasound, which demonstrated an enlarged right testicle, with an inhomogeneous echostructure due to the presence of a hypoechoic area in the middle and upper portion of the testicle. Color Doppler ultrasound did not show signals of intralesional vascularization. The lesion, although having characteristics compatible with hematoma, must not be diagnosed as testicular neoplasia, segmental infarction, or other mimics. For more information, a CEUS examination was performed. The examination clearly showed the extent of the lesion, the integrity of the testicular capsule, and the absence of internal vascularization; all these findings were regarded as indicators of a testicular hematoma. After the urological examination, the patient was prescribed antibiotic therapy and bed rest. For further confirmation of the CEUS examination, an MR was performed 2 days later, showing a perfect correspondence with the CEUS findings. Our case demonstrates that CEUS is a faster, cheaper, and valid alternative to MR in an emergency setting, as in testicular trauma, in which the hematoma may mimic conditions (neoplasm) that require a different treatment.

Fusion Imaging of Contrast-enhanced Ultrasound With CT or MRI for Kidney Lesions

AIM

To evaluate the feasibility of ultrasound (US) computed tomography (CT) or magnetic resonance imaging (MRI) fusion imaging (FI) for localization and assessment of kidney lesions.

MATERIALS AND METHODS

Twenty-eight patients with kidney lesions previously detected on CT or MRI were included in this retrospective study. All 28 patients with kidney lesions, which were indefinable (42.9%) or hard to localize (57.1%) on gray-scale US alone, underwent FI of US with CT/MRI datasets. In 23 (82%) patients with indeterminate kidney lesions, FI including contrast-enhanced US was conducted.

RESULTS

FI was successfully performed in 25 out of 28 (89.3%) patients. FI with contrast-enhanced US was able to clarify the previously detected kidney lesions in 21 out of 23 patients (91.3%).

CONCLUSION

FI is a feasible technique for localizing kidney lesions that are hard to define by grayscale US alone and the additional application of contrast-enhanced US is useful in clarifying indeterminate CT or MRI findings.

Emergency and critical care applications for contrast-enhanced ultrasound

INTRODUCTION

Contrast-enhanced ultrasound (CEUS) using intravascular microbubbles has potential to revolutionize point-of-care ultrasonography by expanding the use of ultrasonography into clinical scenarios previously reserved for computed tomography (CT), magnetic resonance imaging, or angiography.

METHODS

We performed a literature search and report clinical experience to provide an introduction to CEUS and describe its current applications for point-of-care indications.

RESULTS

The uses of CEUS include several applications highly relevant for emergency medicine, such as solid-organ injuries, actively bleeding hematomas, or abdominal aortic aneurysms. Compared with CT as the preeminent advanced imaging modality in the emergency department, CEUS is low cost, radiation sparing, repeatable, and readily available. It does not require sedation, preprocedural laboratory assessment, or transportation to the radiology suite.

CONCLUSIONS

CEUS is a promising imaging technique for point-of-care applications in pediatric and adult patients and can be applied for patients with allergy to CT contrast medium or with impaired renal function. More high-quality CEUS research focusing on accuracy, patient safety, health care costs, and throughput times is needed to validate its use in emergency and critical care settings.

Multiparametric US for scrotal diseases

Multiparametric US is increasingly recognized as a valuable problem-solving technique in scrotal pathologies. Compared to conventional Doppler modes, contrast-enhanced ultrasonography (CEUS) has higher sensitivity in assessing the presence or absence of flows, and to improve differentiation between poorly vascularized tumors and non-neoplastic, avascular lesions. Characterization of benign and malignant complex cysts is improved. In trauma patients, CEUS can help evaluating the viability of testicular parenchyma. In patients with severe epididymo-orchitis, it allows unequivocal assessment of post-inflammatory ischemic changes and abscess formation. CEUS does not add significantly to conventional Doppler modes in spermatic cord torsion. Attempt of differentiating benign and malignant tumors remains a research tool. In the clinical practice, elastography has a limited role for tumor characterization. The majority of malignant tumors are stiff at elastography, but they may display soft areas, or appear globally soft. A quantitative evaluation of testicular stiffness is feasible using shear-wave elastography. Potential clinical applications for elastographic modes could include work-up of infertile patients.

Dynamics of the phospholipid shell of microbubbles: a fluorescence photoselection and spectral phasor approach

The lipid organization of microbubbles is important in many applications.

Contrast-enhanced ultrasound: A promising method for renal microvascular perfusion evaluation

This article reviews the application of contrast-enhanced ultrasound (CEUS) in gauging renal microvascular perfusion in diverse renal diseases. The unique nature of the contrast agents used in CEUS provides real-time and quantitative imaging of the vasculature. In addition to the traditional use of CEUS for evaluation of kidney masses, it also emerges as a safe and effective imaging approach to assess microvascular perfusion in diffuse renal lesions, non-invasively. Although the precise CEUS parameters that may best predict disease still warrant systematic evaluation, animal models and limited clinical trials in humans raise hopes that CEUS could outcompete competing modalities as a first-line tool for assessing renal perfusion non-invasively, even in ailments such as acute kidney injury and chronic kidney disease.

Quantitative evaluation of contrast-enhanced ultrasound for differentiation of renal cell carcinoma subtypes and angiomyolipoma

PURPOSE

To investigate the value of quantitative parameters of contrast-enhanced ultrasound (CEUS) in the differentiation of subtypes of renal cell carcinoma (RCC) and angiomyolipoma (AML).

METHODS

The quantitative characteristics of 341 RCCs and 88 AMLs were analyzed with quantitative software (SonoLiver). Quantitative analysis was conducted in the whole tumor (ROItumor) and the maximum enhanced area of the tumor (ROImax), acquiring the parameters of maximum intensity (IMAX), rise time (RT), time to peak (TTP), mean transit time (mTT), and area under the curve (AUC), were derived and analyzed. The difference values between ROImax and normal renal cortex (ΔPar.s, including ΔIMAX, ΔRT, ΔTTP, ΔmTT, ΔAUC) were compared among renal histotypes.

RESULTS

All time-related parameters (including RT, TTP and mTT) of ROImax were shorter than the corresponding parameters of ROItumor in RCC subtypes (all p<0.05), but made no statistical difference in AMLs (all p>0.05). There were significant differences of all ΔPar.s among RCC subtypes and AML (all p<0.01). ΔIMAX and ΔAUC showed the trend that ccRCC>AML>pRCC=chRCC. ΔTTP showed AML=pRCC=chRCC>ccRCC, ΔRT and ΔmTT showed AML>pRCC=chRCC=ccRCC. ΔmTT could distinguish RCC from AML with the area under the ROC curve (AUC) of 0.86. The AUC of ΔIMAX and ΔAUC was 0.89 and 0.92 vs 0.85 and 0.85 for discriminating between pRCC (or chRCC) and AML vs ccRCC and AML.

CONCLUSIONS

Quantitative analysis of CEUS is a useful modality in AML and RCC subtypes' differentiation, by using ΔmTT, ΔIMAX and ΔAUC.

Emergency radiology

US has a relevant role in the initial assessment of non-traumatic emergencies of the abdomen, sometimes being conclusive and some other times for selecting the patients for further imaging with CT. Injection of a contrast medium may give to the radiologist additional information to that obtained at baseline US and Doppler examination, since real-time, contrast-enhanced US (CEUS) may allow observing findings in the abdomen not recognizable at baseline US or even at color Doppler imaging. Extravascular use of microbubbles may also be useful in clinical practice to rapidly solve a number of unclear aspects. CEUS has a number of distinct advantages in acute patients, including its quickness, low invasiveness, and its possible bedside use. The information based on contrast enhancement is useful for initial diagnosis, therapeutic decision making, and follow-up of the critically ill patients. The purpose of this review is to illustrate the possibilities and limitations of abdominal CEUS in the acute setting, with special emphasis on the detection and characterization of acute inflammatory processes, infarcts, and hemorrhages.

Bedside contrast-enhanced sonography of critically ill patients

The transfer of critically ill patients to the radiology department is, in itself, potentially dangerous, so radiologists are frequently asked to perform bedside sonographic studies in the intensive care unit, surgical or medical department, sterile area, and operating room. In these circumstances, injection of a contrast agent may give the radiologist relevant additional information, which is useful for diagnosis and for better therapeutic management of these critically ill patients. Contrast-enhanced sonography may allow detection of findings not recognizable on baseline sonography or even color Doppler imaging. In this pictorial essay, we highlight the value of real-time contrast-enhanced sonography when performed at the bedside in critically ill patients.

The role of CEUS in the assessment of haemodynamically stable patients with blunt abdominal trauma

Computed tomography (CT) still represents the preferred imaging method in the assessment of patients presenting with multiple trauma. Nevertheless, in patients with low-energy abdominal trauma, the use of CT is debated because of the possible unnecessary radiation exposure. Accordingly, conventional ultrasound (US) imaging has been increasingly employed as the initial imaging modality in the workup of minor traumatic emergency conditions. Focused assessment with sonography for trauma is widely used to detect free intra-abdominal fluid, but its role is controversial, because the absence of free fluid does not exclude the presence of injuries to abdominal organ. Injection of an ultrasound contrast agent (UCA) may give the radiologist relevant additional information to that obtained with conventional US. Thus, in trauma patients, following early assessment with conventional US imaging, a contrast-enhanced US (CEUS) can provide a more reliable evaluation of solid organ injuries and related vascular complications, including active bleeding, pseudoaneurysms, and artero-venous fistulas. CEUS cannot replace abdominal CT, but it represents a noninvasive and repeatable imaging tool capable of providing a reliable assessment of trauma severity and expedite the patient's treatment.

Nuking the radiation: minimizing radiation exposure in the evaluation of pediatric blunt trauma

PURPOSE OF REVIEW

Our objective is to highlight recent literature investigating low-radiation diagnostic strategies in the evaluation of pediatric trauma.

RECENT FINDINGS

In the area of minor head injury, research has focused on implementation of validated clinical decision rules into practice to reduce unnecessary computed tomography scans. Clinical observation may also serve as an adjunct to initial assessment and a potential substitute for computed tomography imaging. Subgroups of children with special needs or severe injury mechanisms may also be safely characterized by the clinical decision rule and spared radiation exposure. Physical examination techniques may be useful in diagnosing mandibular fractures. In addition, evidence suggests that plain radiography for evaluation of blunt thoracic trauma may be sufficient in many cases, and computed tomography could be reserved for those with abnormal radiographs, high-risk mechanisms, or abnormal physical findings. Clinical decision rules are able to predict intra-abdominal injury with high sensitivity. Data suggest that skeletal surveys may be modified to limit radiation exposure in the case of suspected nonaccidental trauma.

SUMMARY

More research is needed in development of pediatric-specific clinical decision rules and risk stratification and in testing low-radiation diagnostic modalities in the pediatric trauma population.

Emergency contrast-enhanced ultrasonography for pancreatic injuries in blunt abdominal trauma

PURPOSE

The purpose of this study was to retrospectively investigate the application of emergency contrast-enhanced ultrasonography (CEUS) in blunt pancreatic trauma.

MATERIALS AND METHODS

Twenty-two consecutive patients with blunt pancreatic trauma were examined using CEUS from March 2007 to June 2012. The findings of CEUS were compared with those of contrast-enhanced computed tomography scans at level-1 diagnostic tests.

RESULTS

Out of the 22 patients, 21 were diagnosed with blunt pancreatic injury using CEUS, including 8 patients with lesions in the neck of pancreas, 9 in the body, 3 in the tail and 1 in the head. The injury sites appeared as anechoic and/or hypoechoic perfusion defect regions with irregular borders in parenchyma and capsule on CEUS images. The lesion sizes measured by CEUS were 1.88 ± 0.81 cm, which were consistent with the 1.93 ± 0.77 cm measured by CT (p > 0.05). Using CT as a reference standard, the detection rate of CEUS in blunt pancreatic trauma was 95.5 % (21/22).

CONCLUSIONS

CEUS findings can be used to provide a reliable diagnosis for blunt pancreatic trauma. CEUS is thus promising in the assessment of blunt pancreatic trauma, especially in institutions where emergency CEUS is used as an initial diagnostic instrument.

Contrast enhanced ultrasound of the kidneys: what is it capable of?

One of the many imaging uses of contrast enhanced ultrasound (CEUS) is studying a wide variety of kidney pathology, due to its ability to detect microvascular blood flow in real time without affecting renal function. CEUS enables dynamic assessment and quantification of microvascularisation up to capillary perfusion. The objective of this paper is to briefly refresh basic knowledge of ultrasound (US) contrast agents' physical properties, to study technical details of CEUS scanning in the kidneys, and to review the commonest renal indications for CEUS, with imaging examples in comparison to baseline unenhanced US and computed tomography when performed. Safety matters and limitations of CEUS of the kidneys are also discussed.